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Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 35 to 42.  Biological diversity has become widely recognized as a critical conservation issue only in the past two decades. The rapid destruction of the tropical rain forests, which are the ecosystems with the highest known species diversity on Earth, has awakened people to the importance and fragility of biological diversity. The high rate of species extinctions in these environments is jolting, but it is important to recognize the significance of biological diversity in all ecosystems. As the human population continues to expand, it will negatively affect one after another of Earth’s ecosystems. In terrestrial ecosystems and in fringe marine ecosystems (such as wetlands), the most common problem is habitat destruction. In most situations, the result is irreversible. Now humans are beginning to destroy marine ecosystems through other types of activities, such as disposal and runoff of poisonous waste; in less than two centuries, by significantly reducing the variety of species on Earth, they have irrevocably redirected the course of evolution.  Certainly, there have been periods in Earth’s history when mass extinctions have occurred. The extinction of the dinosaurs was caused by some physical event, either climatic or cosmic. There have also been less dramatic extinctions, as when natural competition between species reached an extreme conclusion. Only 0.01 percent of the species that have lived on Earth have survived to the present, and it was largely chance that determined which species survived and which died out.  However, nothing has ever equaled the magnitude and speed with which the human species is altering the physical and chemical world and demolishing the environment. In fact, there is wide agreement that it is the rate of change humans are inflicting, even more than the changes themselves, that will lead to biological devastation. Life on Earth has continually been in flux as slow physical and chemical changes have occurred on Earth, but life needs time to adapt-time for migration and genetic adaptation within existing species and time for the proliferation of new genetic material and new species that may be able to survive in new environments. The author mentions all of the following as examples of the effect of humans on the world’s ecosystems EXCEPT _____________ .

Xem chi tiết 432 lượt xem 5 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 35 to 42.  Biological diversity has become widely recognized as a critical conservation issue only in the past two decades. The rapid destruction of the tropical rain forests, which are the ecosystems with the highest known species diversity on Earth, has awakened people to the importance and fragility of biological diversity. The high rate of species extinctions in these environments is jolting, but it is important to recognize the significance of biological diversity in all ecosystems. As the human population continues to expand, it will negatively affect one after another of Earth’s ecosystems. In terrestrial ecosystems and in fringe marine ecosystems (such as wetlands), the most common problem is habitat destruction. In most situations, the result is irreversible. Now humans are beginning to destroy marine ecosystems through other types of activities, such as disposal and runoff of poisonous waste; in less than two centuries, by significantly reducing the variety of species on Earth, they have irrevocably redirected the course of evolution.  Certainly, there have been periods in Earth’s history when mass extinctions have occurred. The extinction of the dinosaurs was caused by some physical event, either climatic or cosmic. There have also been less dramatic extinctions, as when natural competition between species reached an extreme conclusion. Only 0.01 percent of the species that have lived on Earth have survived to the present, and it was largely chance that determined which species survived and which died out.  However, nothing has ever equaled the magnitude and speed with which the human species is altering the physical and chemical world and demolishing the environment. In fact, there is wide agreement that it is the rate of change humans are inflicting, even more than the changes themselves, that will lead to biological devastation. Life on Earth has continually been in flux as slow physical and chemical changes have occurred on Earth, but life needs time to adapt-time for migration and genetic adaptation within existing species and time for the proliferation of new genetic material and new species that may be able to survive in new environments. The author mentions the reduction of the variety of species on Earth in line 7-8 to suggest that

Xem chi tiết 389 lượt xem 5 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 35 to 42.  Biological diversity has become widely recognized as a critical conservation issue only in the past two decades. The rapid destruction of the tropical rain forests, which are the ecosystems with the highest known species diversity on Earth, has awakened people to the importance and fragility of biological diversity. The high rate of species extinctions in these environments is jolting, but it is important to recognize the significance of biological diversity in all ecosystems. As the human population continues to expand, it will negatively affect one after another of Earth’s ecosystems. In terrestrial ecosystems and in fringe marine ecosystems (such as wetlands), the most common problem is habitat destruction. In most situations, the result is irreversible. Now humans are beginning to destroy marine ecosystems through other types of activities, such as disposal and runoff of poisonous waste; in less than two centuries, by significantly reducing the variety of species on Earth, they have irrevocably redirected the course of evolution.  Certainly, there have been periods in Earth’s history when mass extinctions have occurred. The extinction of the dinosaurs was caused by some physical event, either climatic or cosmic. There have also been less dramatic extinctions, as when natural competition between species reached an extreme conclusion. Only 0.01 percent of the species that have lived on Earth have survived to the present, and it was largely chance that determined which species survived and which died out.  However, nothing has ever equaled the magnitude and speed with which the human species is altering the physical and chemical world and demolishing the environment. In fact, there is wide agreement that it is the rate of change humans are inflicting, even more than the changes themselves, that will lead to biological devastation. Life on Earth has continually been in flux as slow physical and chemical changes have occurred on Earth, but life needs time to adapt-time for migration and genetic adaptation within existing species and time for the proliferation of new genetic material and new species that may be able to survive in new environments. The word “jolting” is closest in meaning to _____.

Xem chi tiết 380 lượt xem 5 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 35 to 42.  Biological diversity has become widely recognized as a critical conservation issue only in the past two decades. The rapid destruction of the tropical rain forests, which are the ecosystems with the highest known species diversity on Earth, has awakened people to the importance and fragility of biological diversity. The high rate of species extinctions in these environments is jolting, but it is important to recognize the significance of biological diversity in all ecosystems. As the human population continues to expand, it will negatively affect one after another of Earth’s ecosystems. In terrestrial ecosystems and in fringe marine ecosystems (such as wetlands), the most common problem is habitat destruction. In most situations, the result is irreversible. Now humans are beginning to destroy marine ecosystems through other types of activities, such as disposal and runoff of poisonous waste; in less than two centuries, by significantly reducing the variety of species on Earth, they have irrevocably redirected the course of evolution.  Certainly, there have been periods in Earth’s history when mass extinctions have occurred. The extinction of the dinosaurs was caused by some physical event, either climatic or cosmic. There have also been less dramatic extinctions, as when natural competition between species reached an extreme conclusion. Only 0.01 percent of the species that have lived on Earth have survived to the present, and it was largely chance that determined which species survived and which died out.  However, nothing has ever equaled the magnitude and speed with which the human species is altering the physical and chemical world and demolishing the environment. In fact, there is wide agreement that it is the rate of change humans are inflicting, even more than the changes themselves, that will lead to biological devastation. Life on Earth has continually been in flux as slow physical and chemical changes have occurred on Earth, but life needs time to adapt-time for migration and genetic adaptation within existing species and time for the proliferation of new genetic material and new species that may be able to survive in new environments. What does the passage mainly discuss?

Xem chi tiết 402 lượt xem 5 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 28 to 34.  It is said that George Washington was one of the first to realize how important the building of canals would be to the nation’s development. In fact, before he became the President, he headed the first company in the United States to build a canal, which was to connect the Ohio and Potomac rivers. It was never completed, but it showed the nation the feasibility of canals. As the country expanded westward, settlers in western New York, Pennsylvania, and Ohio needed a means to ship goods. Canals linking natural waterways seemed to supply an effective method.  In 1791, engineers commissioned by the state of New York investigated the possibility of a canal between Albany on the Hudson River and Buffalo on Lake Eric to link the Great Lakes area with the Atlantic seacoast. It would avoid the mountains that served as a barrier to canals from the Delaware and Potomac rivers.  The first attempt to dig the canal, to be called the Eric Canal, was made by private companies but only a comparatively small portion was built before the project was halted for lack of funds. The cost of the prospect was estimated $5 million, an enormous amount for those days. There was some on-again-off-again federal funding, but this time the War of 1812 put an end to construction. In 1817, DeWitt Clinton was elected Governor of New York and persuaded the state to finance and build the canal. It was completed in 1825, costing $2 million more than expected.  The canal rapidly lived up to its sponsors’ faith, quickly paying for itself through tolls. It was far more economical than any other form of transportation at the time. It permitted trade between the Great Lake region and the East coast, robbing the Mississippi River of much of its traffic. It allowed New York to supplant Boston, Philadelphia, and other eastern cities as the chief center of both domestic and foreign commerce. Cities sprang up along the canal. It also contributed in a number of ways to the North’s victory over the South in the Civil War.  An expansion of the canal was planned in 1849. Increased traffic would undoubtedly have warranted its construction had it not been for the railroads. Which of the following is NOT given as an effect of the building of the Eric Canal in paragraph 4?

Xem chi tiết 395 lượt xem 5 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 28 to 34.  It is said that George Washington was one of the first to realize how important the building of canals would be to the nation’s development. In fact, before he became the President, he headed the first company in the United States to build a canal, which was to connect the Ohio and Potomac rivers. It was never completed, but it showed the nation the feasibility of canals. As the country expanded westward, settlers in western New York, Pennsylvania, and Ohio needed a means to ship goods. Canals linking natural waterways seemed to supply an effective method.  In 1791, engineers commissioned by the state of New York investigated the possibility of a canal between Albany on the Hudson River and Buffalo on Lake Eric to link the Great Lakes area with the Atlantic seacoast. It would avoid the mountains that served as a barrier to canals from the Delaware and Potomac rivers.  The first attempt to dig the canal, to be called the Eric Canal, was made by private companies but only a comparatively small portion was built before the project was halted for lack of funds. The cost of the prospect was estimated $5 million, an enormous amount for those days. There was some on-again-off-again federal funding, but this time the War of 1812 put an end to construction. In 1817, DeWitt Clinton was elected Governor of New York and persuaded the state to finance and build the canal. It was completed in 1825, costing $2 million more than expected.  The canal rapidly lived up to its sponsors’ faith, quickly paying for itself through tolls. It was far more economical than any other form of transportation at the time. It permitted trade between the Great Lake region and the East coast, robbing the Mississippi River of much of its traffic. It allowed New York to supplant Boston, Philadelphia, and other eastern cities as the chief center of both domestic and foreign commerce. Cities sprang up along the canal. It also contributed in a number of ways to the North’s victory over the South in the Civil War.  An expansion of the canal was planned in 1849. Increased traffic would undoubtedly have warranted its construction had it not been for the railroads. The word “tolls” in paragraph 4 is closest in meaning to which of the following?

Xem chi tiết 367 lượt xem 5 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 28 to 34.  It is said that George Washington was one of the first to realize how important the building of canals would be to the nation’s development. In fact, before he became the President, he headed the first company in the United States to build a canal, which was to connect the Ohio and Potomac rivers. It was never completed, but it showed the nation the feasibility of canals. As the country expanded westward, settlers in western New York, Pennsylvania, and Ohio needed a means to ship goods. Canals linking natural waterways seemed to supply an effective method.  In 1791, engineers commissioned by the state of New York investigated the possibility of a canal between Albany on the Hudson River and Buffalo on Lake Eric to link the Great Lakes area with the Atlantic seacoast. It would avoid the mountains that served as a barrier to canals from the Delaware and Potomac rivers.  The first attempt to dig the canal, to be called the Eric Canal, was made by private companies but only a comparatively small portion was built before the project was halted for lack of funds. The cost of the prospect was estimated $5 million, an enormous amount for those days. There was some on-again-off-again federal funding, but this time the War of 1812 put an end to construction. In 1817, DeWitt Clinton was elected Governor of New York and persuaded the state to finance and build the canal. It was completed in 1825, costing $2 million more than expected.  The canal rapidly lived up to its sponsors’ faith, quickly paying for itself through tolls. It was far more economical than any other form of transportation at the time. It permitted trade between the Great Lake region and the East coast, robbing the Mississippi River of much of its traffic. It allowed New York to supplant Boston, Philadelphia, and other eastern cities as the chief center of both domestic and foreign commerce. Cities sprang up along the canal. It also contributed in a number of ways to the North’s victory over the South in the Civil War.  An expansion of the canal was planned in 1849. Increased traffic would undoubtedly have warranted its construction had it not been for the railroads. The actual cost of building the Eric Canal was ____.

Xem chi tiết 395 lượt xem 5 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 28 to 34.  It is said that George Washington was one of the first to realize how important the building of canals would be to the nation’s development. In fact, before he became the President, he headed the first company in the United States to build a canal, which was to connect the Ohio and Potomac rivers. It was never completed, but it showed the nation the feasibility of canals. As the country expanded westward, settlers in western New York, Pennsylvania, and Ohio needed a means to ship goods. Canals linking natural waterways seemed to supply an effective method.  In 1791, engineers commissioned by the state of New York investigated the possibility of a canal between Albany on the Hudson River and Buffalo on Lake Eric to link the Great Lakes area with the Atlantic seacoast. It would avoid the mountains that served as a barrier to canals from the Delaware and Potomac rivers.  The first attempt to dig the canal, to be called the Eric Canal, was made by private companies but only a comparatively small portion was built before the project was halted for lack of funds. The cost of the prospect was estimated $5 million, an enormous amount for those days. There was some on-again-off-again federal funding, but this time the War of 1812 put an end to construction. In 1817, DeWitt Clinton was elected Governor of New York and persuaded the state to finance and build the canal. It was completed in 1825, costing $2 million more than expected.  The canal rapidly lived up to its sponsors’ faith, quickly paying for itself through tolls. It was far more economical than any other form of transportation at the time. It permitted trade between the Great Lake region and the East coast, robbing the Mississippi River of much of its traffic. It allowed New York to supplant Boston, Philadelphia, and other eastern cities as the chief center of both domestic and foreign commerce. Cities sprang up along the canal. It also contributed in a number of ways to the North’s victory over the South in the Civil War.  An expansion of the canal was planned in 1849. Increased traffic would undoubtedly have warranted its construction had it not been for the railroads. The completion of the Eric Canal was financed by ______.

Xem chi tiết 428 lượt xem 5 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 28 to 34.  It is said that George Washington was one of the first to realize how important the building of canals would be to the nation’s development. In fact, before he became the President, he headed the first company in the United States to build a canal, which was to connect the Ohio and Potomac rivers. It was never completed, but it showed the nation the feasibility of canals. As the country expanded westward, settlers in western New York, Pennsylvania, and Ohio needed a means to ship goods. Canals linking natural waterways seemed to supply an effective method.  In 1791, engineers commissioned by the state of New York investigated the possibility of a canal between Albany on the Hudson River and Buffalo on Lake Eric to link the Great Lakes area with the Atlantic seacoast. It would avoid the mountains that served as a barrier to canals from the Delaware and Potomac rivers.  The first attempt to dig the canal, to be called the Eric Canal, was made by private companies but only a comparatively small portion was built before the project was halted for lack of funds. The cost of the prospect was estimated $5 million, an enormous amount for those days. There was some on-again-off-again federal funding, but this time the War of 1812 put an end to construction. In 1817, DeWitt Clinton was elected Governor of New York and persuaded the state to finance and build the canal. It was completed in 1825, costing $2 million more than expected.  The canal rapidly lived up to its sponsors’ faith, quickly paying for itself through tolls. It was far more economical than any other form of transportation at the time. It permitted trade between the Great Lake region and the East coast, robbing the Mississippi River of much of its traffic. It allowed New York to supplant Boston, Philadelphia, and other eastern cities as the chief center of both domestic and foreign commerce. Cities sprang up along the canal. It also contributed in a number of ways to the North’s victory over the South in the Civil War.  An expansion of the canal was planned in 1849. Increased traffic would undoubtedly have warranted its construction had it not been for the railroads. According to the passage, the Eric Canal connected the _________.

Xem chi tiết 392 lượt xem 5 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 28 to 34.  It is said that George Washington was one of the first to realize how important the building of canals would be to the nation’s development. In fact, before he became the President, he headed the first company in the United States to build a canal, which was to connect the Ohio and Potomac rivers. It was never completed, but it showed the nation the feasibility of canals. As the country expanded westward, settlers in western New York, Pennsylvania, and Ohio needed a means to ship goods. Canals linking natural waterways seemed to supply an effective method.  In 1791, engineers commissioned by the state of New York investigated the possibility of a canal between Albany on the Hudson River and Buffalo on Lake Eric to link the Great Lakes area with the Atlantic seacoast. It would avoid the mountains that served as a barrier to canals from the Delaware and Potomac rivers.  The first attempt to dig the canal, to be called the Eric Canal, was made by private companies but only a comparatively small portion was built before the project was halted for lack of funds. The cost of the prospect was estimated $5 million, an enormous amount for those days. There was some on-again-off-again federal funding, but this time the War of 1812 put an end to construction. In 1817, DeWitt Clinton was elected Governor of New York and persuaded the state to finance and build the canal. It was completed in 1825, costing $2 million more than expected.  The canal rapidly lived up to its sponsors’ faith, quickly paying for itself through tolls. It was far more economical than any other form of transportation at the time. It permitted trade between the Great Lake region and the East coast, robbing the Mississippi River of much of its traffic. It allowed New York to supplant Boston, Philadelphia, and other eastern cities as the chief center of both domestic and foreign commerce. Cities sprang up along the canal. It also contributed in a number of ways to the North’s victory over the South in the Civil War.  An expansion of the canal was planned in 1849. Increased traffic would undoubtedly have warranted its construction had it not been for the railroads. The word “feasibility” in paragraph 1 is closest in meaning to _______.

Xem chi tiết 510 lượt xem 5 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 28 to 34.  It is said that George Washington was one of the first to realize how important the building of canals would be to the nation’s development. In fact, before he became the President, he headed the first company in the United States to build a canal, which was to connect the Ohio and Potomac rivers. It was never completed, but it showed the nation the feasibility of canals. As the country expanded westward, settlers in western New York, Pennsylvania, and Ohio needed a means to ship goods. Canals linking natural waterways seemed to supply an effective method.  In 1791, engineers commissioned by the state of New York investigated the possibility of a canal between Albany on the Hudson River and Buffalo on Lake Eric to link the Great Lakes area with the Atlantic seacoast. It would avoid the mountains that served as a barrier to canals from the Delaware and Potomac rivers.  The first attempt to dig the canal, to be called the Eric Canal, was made by private companies but only a comparatively small portion was built before the project was halted for lack of funds. The cost of the prospect was estimated $5 million, an enormous amount for those days. There was some on-again-off-again federal funding, but this time the War of 1812 put an end to construction. In 1817, DeWitt Clinton was elected Governor of New York and persuaded the state to finance and build the canal. It was completed in 1825, costing $2 million more than expected.  The canal rapidly lived up to its sponsors’ faith, quickly paying for itself through tolls. It was far more economical than any other form of transportation at the time. It permitted trade between the Great Lake region and the East coast, robbing the Mississippi River of much of its traffic. It allowed New York to supplant Boston, Philadelphia, and other eastern cities as the chief center of both domestic and foreign commerce. Cities sprang up along the canal. It also contributed in a number of ways to the North’s victory over the South in the Civil War.  An expansion of the canal was planned in 1849. Increased traffic would undoubtedly have warranted its construction had it not been for the railroads. Why does the author most likely mention George Washington in the first paragraph?

Xem chi tiết 0.9 K lượt xem 5 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.        Lighthouses are towers with strong lights that help mariners plot their position, inform them that land is near, and warn them of dangerous rocks and reefs. They are placed at prominent points on the coast and on islands, reefs, and sandbars.       Every lighthouse has a distinctive pattern of light known as its characteristic. There are five basic characteristics: fixed, flashing, occulting, group flashing, and group occulting. A fixed signal is a steady beam. A flashing signal has periods of darkness longer than periods of light, while an occulting signal’s periods of light are longer. A group-flashing light gives off two or more flashes at regular intervals, and a group - occulting signal consists of a fixed light with two or more periods of darkness at regular intervals. Some lighthouses use lights of different colors as well, and today, most lighthouses are also equipped with radio beacons. The three types of apparatus used to produce the signals are the catoptric, in which metal is used to reflect the light; the dioptric, in which glass is used; and the catadioptric, in which both glass and metal are used.        In the daytime, lighthouses can usually be identified by their structure alone. The most typical structure is a tower tapering at the top, but some, such as the Bastion Lighthouse on the Saint Lawrence River, are shaped like pyramids, and others, such as the Race Rock light, look like wooden houses sitting on high platforms. Still others, such as The American Shoal lighthouse off the Florida Coast, are skeletal towers of steel. Where lighthouses might be contused in daylight, they can be distinguished by day- marker patterns - designed of checks and stripes painted in vivid colors on lighthouse walls.       In the past, the job of lighthouse keeper was lonely and difficult if somewhat romantic. Lighthouse keepers put in hours of tedious work maintaining the lights. Today, lighthouses are almost entirely automated with humans supplying only occasional maintenance. Because of improvements in navigational technology, the importance of lighthouses has diminished. There are only about 340 functioning lighthouses in existence in the United States today, compared to about 1,500 in 1900, and there are only about 1,400 functioning lighthouses outside the United States. Some decommissioned lighthouses have been preserved as historical monument.The author implies that, compared to those of the past, contemporary lighthouses______.

Xem chi tiết 1.7 K lượt xem 5 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.        Lighthouses are towers with strong lights that help mariners plot their position, inform them that land is near, and warn them of dangerous rocks and reefs. They are placed at prominent points on the coast and on islands, reefs, and sandbars.       Every lighthouse has a distinctive pattern of light known as its characteristic. There are five basic characteristics: fixed, flashing, occulting, group flashing, and group occulting. A fixed signal is a steady beam. A flashing signal has periods of darkness longer than periods of light, while an occulting signal’s periods of light are longer. A group-flashing light gives off two or more flashes at regular intervals, and a group - occulting signal consists of a fixed light with two or more periods of darkness at regular intervals. Some lighthouses use lights of different colors as well, and today, most lighthouses are also equipped with radio beacons. The three types of apparatus used to produce the signals are the catoptric, in which metal is used to reflect the light; the dioptric, in which glass is used; and the catadioptric, in which both glass and metal are used.        In the daytime, lighthouses can usually be identified by their structure alone. The most typical structure is a tower tapering at the top, but some, such as the Bastion Lighthouse on the Saint Lawrence River, are shaped like pyramids, and others, such as the Race Rock light, look like wooden houses sitting on high platforms. Still others, such as The American Shoal lighthouse off the Florida Coast, are skeletal towers of steel. Where lighthouses might be contused in daylight, they can be distinguished by day- marker patterns - designed of checks and stripes painted in vivid colors on lighthouse walls.       In the past, the job of lighthouse keeper was lonely and difficult if somewhat romantic. Lighthouse keepers put in hours of tedious work maintaining the lights. Today, lighthouses are almost entirely automated with humans supplying only occasional maintenance. Because of improvements in navigational technology, the importance of lighthouses has diminished. There are only about 340 functioning lighthouses in existence in the United States today, compared to about 1,500 in 1900, and there are only about 1,400 functioning lighthouses outside the United States. Some decommissioned lighthouses have been preserved as historical monument.The word “tapering” is closest in meaning to which of the following?

Xem chi tiết 542 lượt xem 5 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.        Lighthouses are towers with strong lights that help mariners plot their position, inform them that land is near, and warn them of dangerous rocks and reefs. They are placed at prominent points on the coast and on islands, reefs, and sandbars.       Every lighthouse has a distinctive pattern of light known as its characteristic. There are five basic characteristics: fixed, flashing, occulting, group flashing, and group occulting. A fixed signal is a steady beam. A flashing signal has periods of darkness longer than periods of light, while an occulting signal’s periods of light are longer. A group-flashing light gives off two or more flashes at regular intervals, and a group - occulting signal consists of a fixed light with two or more periods of darkness at regular intervals. Some lighthouses use lights of different colors as well, and today, most lighthouses are also equipped with radio beacons. The three types of apparatus used to produce the signals are the catoptric, in which metal is used to reflect the light; the dioptric, in which glass is used; and the catadioptric, in which both glass and metal are used.        In the daytime, lighthouses can usually be identified by their structure alone. The most typical structure is a tower tapering at the top, but some, such as the Bastion Lighthouse on the Saint Lawrence River, are shaped like pyramids, and others, such as the Race Rock light, look like wooden houses sitting on high platforms. Still others, such as The American Shoal lighthouse off the Florida Coast, are skeletal towers of steel. Where lighthouses might be contused in daylight, they can be distinguished by day- marker patterns - designed of checks and stripes painted in vivid colors on lighthouse walls.       In the past, the job of lighthouse keeper was lonely and difficult if somewhat romantic. Lighthouse keepers put in hours of tedious work maintaining the lights. Today, lighthouses are almost entirely automated with humans supplying only occasional maintenance. Because of improvements in navigational technology, the importance of lighthouses has diminished. There are only about 340 functioning lighthouses in existence in the United States today, compared to about 1,500 in 1900, and there are only about 1,400 functioning lighthouses outside the United States. Some decommissioned lighthouses have been preserved as historical monument.For which of the following does the author NOT provide a scientific example in the third paragraph?

Xem chi tiết 1.6 K lượt xem 5 năm trước

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.        Lighthouses are towers with strong lights that help mariners plot their position, inform them that land is near, and warn them of dangerous rocks and reefs. They are placed at prominent points on the coast and on islands, reefs, and sandbars.       Every lighthouse has a distinctive pattern of light known as its characteristic. There are five basic characteristics: fixed, flashing, occulting, group flashing, and group occulting. A fixed signal is a steady beam. A flashing signal has periods of darkness longer than periods of light, while an occulting signal’s periods of light are longer. A group-flashing light gives off two or more flashes at regular intervals, and a group - occulting signal consists of a fixed light with two or more periods of darkness at regular intervals. Some lighthouses use lights of different colors as well, and today, most lighthouses are also equipped with radio beacons. The three types of apparatus used to produce the signals are the catoptric, in which metal is used to reflect the light; the dioptric, in which glass is used; and the catadioptric, in which both glass and metal are used.        In the daytime, lighthouses can usually be identified by their structure alone. The most typical structure is a tower tapering at the top, but some, such as the Bastion Lighthouse on the Saint Lawrence River, are shaped like pyramids, and others, such as the Race Rock light, look like wooden houses sitting on high platforms. Still others, such as The American Shoal lighthouse off the Florida Coast, are skeletal towers of steel. Where lighthouses might be contused in daylight, they can be distinguished by day- marker patterns - designed of checks and stripes painted in vivid colors on lighthouse walls.       In the past, the job of lighthouse keeper was lonely and difficult if somewhat romantic. Lighthouse keepers put in hours of tedious work maintaining the lights. Today, lighthouses are almost entirely automated with humans supplying only occasional maintenance. Because of improvements in navigational technology, the importance of lighthouses has diminished. There are only about 340 functioning lighthouses in existence in the United States today, compared to about 1,500 in 1900, and there are only about 1,400 functioning lighthouses outside the United States. Some decommissioned lighthouses have been preserved as historical monument.According to the passage, a catoptric apparatus is one that uses_________.

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Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.        Lighthouses are towers with strong lights that help mariners plot their position, inform them that land is near, and warn them of dangerous rocks and reefs. They are placed at prominent points on the coast and on islands, reefs, and sandbars.       Every lighthouse has a distinctive pattern of light known as its characteristic. There are five basic characteristics: fixed, flashing, occulting, group flashing, and group occulting. A fixed signal is a steady beam. A flashing signal has periods of darkness longer than periods of light, while an occulting signal’s periods of light are longer. A group-flashing light gives off two or more flashes at regular intervals, and a group - occulting signal consists of a fixed light with two or more periods of darkness at regular intervals. Some lighthouses use lights of different colors as well, and today, most lighthouses are also equipped with radio beacons. The three types of apparatus used to produce the signals are the catoptric, in which metal is used to reflect the light; the dioptric, in which glass is used; and the catadioptric, in which both glass and metal are used.        In the daytime, lighthouses can usually be identified by their structure alone. The most typical structure is a tower tapering at the top, but some, such as the Bastion Lighthouse on the Saint Lawrence River, are shaped like pyramids, and others, such as the Race Rock light, look like wooden houses sitting on high platforms. Still others, such as The American Shoal lighthouse off the Florida Coast, are skeletal towers of steel. Where lighthouses might be contused in daylight, they can be distinguished by day- marker patterns - designed of checks and stripes painted in vivid colors on lighthouse walls.       In the past, the job of lighthouse keeper was lonely and difficult if somewhat romantic. Lighthouse keepers put in hours of tedious work maintaining the lights. Today, lighthouses are almost entirely automated with humans supplying only occasional maintenance. Because of improvements in navigational technology, the importance of lighthouses has diminished. There are only about 340 functioning lighthouses in existence in the United States today, compared to about 1,500 in 1900, and there are only about 1,400 functioning lighthouses outside the United States. Some decommissioned lighthouses have been preserved as historical monument.According to the passage, what kind of signal has long periods of light that are regularly broken by two or more periods of darkness?

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Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.        Lighthouses are towers with strong lights that help mariners plot their position, inform them that land is near, and warn them of dangerous rocks and reefs. They are placed at prominent points on the coast and on islands, reefs, and sandbars.       Every lighthouse has a distinctive pattern of light known as its characteristic. There are five basic characteristics: fixed, flashing, occulting, group flashing, and group occulting. A fixed signal is a steady beam. A flashing signal has periods of darkness longer than periods of light, while an occulting signal’s periods of light are longer. A group-flashing light gives off two or more flashes at regular intervals, and a group - occulting signal consists of a fixed light with two or more periods of darkness at regular intervals. Some lighthouses use lights of different colors as well, and today, most lighthouses are also equipped with radio beacons. The three types of apparatus used to produce the signals are the catoptric, in which metal is used to reflect the light; the dioptric, in which glass is used; and the catadioptric, in which both glass and metal are used.        In the daytime, lighthouses can usually be identified by their structure alone. The most typical structure is a tower tapering at the top, but some, such as the Bastion Lighthouse on the Saint Lawrence River, are shaped like pyramids, and others, such as the Race Rock light, look like wooden houses sitting on high platforms. Still others, such as The American Shoal lighthouse off the Florida Coast, are skeletal towers of steel. Where lighthouses might be contused in daylight, they can be distinguished by day- marker patterns - designed of checks and stripes painted in vivid colors on lighthouse walls.       In the past, the job of lighthouse keeper was lonely and difficult if somewhat romantic. Lighthouse keepers put in hours of tedious work maintaining the lights. Today, lighthouses are almost entirely automated with humans supplying only occasional maintenance. Because of improvements in navigational technology, the importance of lighthouses has diminished. There are only about 340 functioning lighthouses in existence in the United States today, compared to about 1,500 in 1900, and there are only about 1,400 functioning lighthouses outside the United States. Some decommissioned lighthouses have been preserved as historical monument.In the context of this passage, the author uses the term “characteristic” to refer to a_____.

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Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.        Lighthouses are towers with strong lights that help mariners plot their position, inform them that land is near, and warn them of dangerous rocks and reefs. They are placed at prominent points on the coast and on islands, reefs, and sandbars.       Every lighthouse has a distinctive pattern of light known as its characteristic. There are five basic characteristics: fixed, flashing, occulting, group flashing, and group occulting. A fixed signal is a steady beam. A flashing signal has periods of darkness longer than periods of light, while an occulting signal’s periods of light are longer. A group-flashing light gives off two or more flashes at regular intervals, and a group - occulting signal consists of a fixed light with two or more periods of darkness at regular intervals. Some lighthouses use lights of different colors as well, and today, most lighthouses are also equipped with radio beacons. The three types of apparatus used to produce the signals are the catoptric, in which metal is used to reflect the light; the dioptric, in which glass is used; and the catadioptric, in which both glass and metal are used.        In the daytime, lighthouses can usually be identified by their structure alone. The most typical structure is a tower tapering at the top, but some, such as the Bastion Lighthouse on the Saint Lawrence River, are shaped like pyramids, and others, such as the Race Rock light, look like wooden houses sitting on high platforms. Still others, such as The American Shoal lighthouse off the Florida Coast, are skeletal towers of steel. Where lighthouses might be contused in daylight, they can be distinguished by day- marker patterns - designed of checks and stripes painted in vivid colors on lighthouse walls.       In the past, the job of lighthouse keeper was lonely and difficult if somewhat romantic. Lighthouse keepers put in hours of tedious work maintaining the lights. Today, lighthouses are almost entirely automated with humans supplying only occasional maintenance. Because of improvements in navigational technology, the importance of lighthouses has diminished. There are only about 340 functioning lighthouses in existence in the United States today, compared to about 1,500 in 1900, and there are only about 1,400 functioning lighthouses outside the United States. Some decommissioned lighthouses have been preserved as historical monument.Which of the following is NOT mentioned in the passage as one of the functions of lighthouses?

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