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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. William Sydney Porter (1862-1910), who wrote under the pseudonym of O. Henry, was born in North Carolina. His only formal education was to attend his Aunt Lina’s school until the age of fifteen, where he developed his lifelong love of books. By 1881 he was a licensed pharmacist. However, within a year, on the recommendation of a medical colleague of his Father’s, Porter moved to La Salle County in Texas for two years herding sheep. During this time, Webster’s Unabridged Dictionary was his constant companion, and Porter gained a knowledge of ranch life that he later incorporated into many of his short stories. He then moved to Austin for three years, and during this time the first recorded use of his pseudonym appeared, allegedly derived from his habit of calling “Oh, Henry” to a family cat. In 1887, Porter married Athol Estes. He worked as a draftsman, then as a bank teller for the First Nation Bank. In 1894 Porter founded his own humor weekly, the “Rolling Stone”, a venture that failed within a year, and later wrote a column for the Houston Daily Post. In the meantime, the First National Bank was examined, and the subsequent indictment of 1886 stated that Porter had embezzled funds. Porter then fled to New Orleans, and later to Honduras, leaving his wife and child in Austin. He returned in 1897 because of his wife’s continued ill-health, however, she died six months later. Then, in 1898 Porter was found guilty and sentenced to five years imprisonment in Ohio. At the age of thirty- five, he entered prison as a defeated man; he had lost his job, his home, his wife, and finally his freedom. He emerged from prison three years later, reborn as O. Henry, the pseudonym he now used to hide his true identity. He wrote at least twelve stories in jail, and after regaining his freedom, went to New York City, where he published more than 300 stories and gained fame as America’s favorite short story writer. Porter married again in 1907, but after months of poor health, he died in New York City at the age of forty-eight in 1910. O. Henry’s stories have been translated all over the world. Porter lost all of the following when he went to prison EXCEPT his______.

Xem chi tiết 1.3 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. William Sydney Porter (1862-1910), who wrote under the pseudonym of O. Henry, was born in North Carolina. His only formal education was to attend his Aunt Lina’s school until the age of fifteen, where he developed his lifelong love of books. By 1881 he was a licensed pharmacist. However, within a year, on the recommendation of a medical colleague of his Father’s, Porter moved to La Salle County in Texas for two years herding sheep. During this time, Webster’s Unabridged Dictionary was his constant companion, and Porter gained a knowledge of ranch life that he later incorporated into many of his short stories. He then moved to Austin for three years, and during this time the first recorded use of his pseudonym appeared, allegedly derived from his habit of calling “Oh, Henry” to a family cat. In 1887, Porter married Athol Estes. He worked as a draftsman, then as a bank teller for the First Nation Bank. In 1894 Porter founded his own humor weekly, the “Rolling Stone”, a venture that failed within a year, and later wrote a column for the Houston Daily Post. In the meantime, the First National Bank was examined, and the subsequent indictment of 1886 stated that Porter had embezzled funds. Porter then fled to New Orleans, and later to Honduras, leaving his wife and child in Austin. He returned in 1897 because of his wife’s continued ill-health, however, she died six months later. Then, in 1898 Porter was found guilty and sentenced to five years imprisonment in Ohio. At the age of thirty- five, he entered prison as a defeated man; he had lost his job, his home, his wife, and finally his freedom. He emerged from prison three years later, reborn as O. Henry, the pseudonym he now used to hide his true identity. He wrote at least twelve stories in jail, and after regaining his freedom, went to New York City, where he published more than 300 stories and gained fame as America’s favorite short story writer. Porter married again in 1907, but after months of poor health, he died in New York City at the age of forty-eight in 1910. O. Henry’s stories have been translated all over the world. Which of the following is the main topic of the passage?

Xem chi tiết 483 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. "Did you see that?" Joe said to his friend Bill. "You're a great shooter!" Bill caught the basketball and bounced it before throwing it again. The ball flew into the net. "Bill, you never miss!" Joe said admiringly. "Unless I'm in a real game," Bill complained. "Then I miss all the time." Joe knew that Bill was right. Bill performed much better when he was having fun with Joe in the school yard than he did when he was playing for the school team in front of a large crowd. "Maybe you just need to practice more," Joe suggested. "But I practice all the time with you!" Bill objected. He shook his head. "I just can't play well when people are watching me." "You play well when I'm watching," Joe pointed out. "That's because I've known you since we were five years old," Bill said with a smile. "I'm just not comfortable playing when other people are around." Joe nodded and understood, but he also had an idea. The next day Joe and Bill met in the school yard again to practice. After a few minutes, Joe excused himself. "Practice without me," Joe said to his friend. "I'll be back in a minute." Joe hurried through the school building, gathering together whomever he could find—two students, a math teacher, two secretaries, and a janitor. When Joe explained why he needed them, everyone was happy to help. Joe reminded the group to stay quiet as they all went toward the school's basketball court. As Joe had hoped, Bill was still practicing basketball. He made five baskets in a row without noticing the silent people standing behind him. "Hey, Bill!" Joe called out finally. Bill turned. A look of surprise came over his face. "I just wanted to show you that you could play well with people watching you," Joe said. "Now you'll have nothing to worry about for the next game!" At the end of the story, all of the following people watch Bill practice EXCEPT ………………...

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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 word or phrase that best fits each of the numbered blanks. Fill in the appropriate word in question 29 THE FUTURE OF WATER Many of us often wonder what the future holds; some believe major advances in technology will occur which will result in improvements to our everyday lives. Scientists have predicted shortages in fossil fuels and changes in the weather patterns of the world. (25)________, one significant change that will have an alarming impact on all of us is the global water shortage. Analysts have forecast that some of the consequences of this will be mass migration from Africa to Europe and wars between countries over clean water. The main causes of this disturbing water shortage are global warming, climate change and the increasing world population. The supply of fresh water (26) ________ comes from mountain glaciers and flows into lakes and rivers is diminishing, and this also (27)__________ to the shortage. Water analysts and government leaders need to start making radical changes to the way water use is managed and they need to find new sources that will be able to meet the demands of an ever-growing population. In addition, more things need to be done to control global warming as this will help to reduce water shortages. People should be made (28)_______of the situation and warned not to waste water. Multinational companies should invest in developing better water management systems. In summary, if we start (29)_______ action now, we might be able to prevent a world disaster.

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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 word or phrase that best fits each of the numbered blanks. Fill in the appropriate word in question 28 THE FUTURE OF WATER Many of us often wonder what the future holds; some believe major advances in technology will occur which will result in improvements to our everyday lives. Scientists have predicted shortages in fossil fuels and changes in the weather patterns of the world. (25)________, one significant change that will have an alarming impact on all of us is the global water shortage. Analysts have forecast that some of the consequences of this will be mass migration from Africa to Europe and wars between countries over clean water. The main causes of this disturbing water shortage are global warming, climate change and the increasing world population. The supply of fresh water (26) ________ comes from mountain glaciers and flows into lakes and rivers is diminishing, and this also (27)__________ to the shortage. Water analysts and government leaders need to start making radical changes to the way water use is managed and they need to find new sources that will be able to meet the demands of an ever-growing population. In addition, more things need to be done to control global warming as this will help to reduce water shortages. People should be made (28)_______of the situation and warned not to waste water. Multinational companies should invest in developing better water management systems. In summary, if we start (29)_______ action now, we might be able to prevent a world disaster.

Xem chi tiết 2.8 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 word or phrase that best fits each of the numbered blanks. Fill in the appropriate word in question 27 THE FUTURE OF WATER Many of us often wonder what the future holds; some believe major advances in technology will occur which will result in improvements to our everyday lives. Scientists have predicted shortages in fossil fuels and changes in the weather patterns of the world. (25)________, one significant change that will have an alarming impact on all of us is the global water shortage. Analysts have forecast that some of the consequences of this will be mass migration from Africa to Europe and wars between countries over clean water. The main causes of this disturbing water shortage are global warming, climate change and the increasing world population. The supply of fresh water (26) ________ comes from mountain glaciers and flows into lakes and rivers is diminishing, and this also (27)__________ to the shortage. Water analysts and government leaders need to start making radical changes to the way water use is managed and they need to find new sources that will be able to meet the demands of an ever-growing population. In addition, more things need to be done to control global warming as this will help to reduce water shortages. People should be made (28)_______of the situation and warned not to waste water. Multinational companies should invest in developing better water management systems. In summary, if we start (29)_______ action now, we might be able to prevent a world disaster.

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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 word or phrase that best fits each of the numbered blanks. Fill in the appropriate word in question 26 THE FUTURE OF WATER Many of us often wonder what the future holds; some believe major advances in technology will occur which will result in improvements to our everyday lives. Scientists have predicted shortages in fossil fuels and changes in the weather patterns of the world. (25)________, one significant change that will have an alarming impact on all of us is the global water shortage. Analysts have forecast that some of the consequences of this will be mass migration from Africa to Europe and wars between countries over clean water. The main causes of this disturbing water shortage are global warming, climate change and the increasing world population. The supply of fresh water (26) ________ comes from mountain glaciers and flows into lakes and rivers is diminishing, and this also (27)__________ to the shortage. Water analysts and government leaders need to start making radical changes to the way water use is managed and they need to find new sources that will be able to meet the demands of an ever-growing population. In addition, more things need to be done to control global warming as this will help to reduce water shortages. People should be made (28)_______of the situation and warned not to waste water. Multinational companies should invest in developing better water management systems. In summary, if we start (29)_______ action now, we might be able to prevent a world disaster.

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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 word or phrase that best fits each of the numbered blanks. Fill in the appropriate word in question 25 THE FUTURE OF WATER Many of us often wonder what the future holds; some believe major advances in technology will occur which will result in improvements to our everyday lives. Scientists have predicted shortages in fossil fuels and changes in the weather patterns of the world. (25)________, one significant change that will have an alarming impact on all of us is the global water shortage. Analysts have forecast that some of the consequences of this will be mass migration from Africa to Europe and wars between countries over clean water. The main causes of this disturbing water shortage are global warming, climate change and the increasing world population. The supply of fresh water (26) ________ comes from mountain glaciers and flows into lakes and rivers is diminishing, and this also (27)__________ to the shortage. Water analysts and government leaders need to start making radical changes to the way water use is managed and they need to find new sources that will be able to meet the demands of an ever-growing population. In addition, more things need to be done to control global warming as this will help to reduce water shortages. People should be made (28)_______of the situation and warned not to waste water. Multinational companies should invest in developing better water management systems. In summary, if we start (29)_______ action now, we might be able to prevent a world disaster.

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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 Martin Luther King, Jf., is well- known for his work in civil rights and for his many famous speeches, among which is his moving “ I have a dream” speech. But fewer people know much about King’s childhood. M.L., as he was called, was born in 1929 in Atlanta, Georgia, at the home of his maternal grandfather. M.L.’s grandfather purchased their home on Auburn Avenue in 1909, twenty years before M.L was born. His grandfather allowed the house to be used as a meeting place for a number of organizations dedicated to the education and social advancement of blacks. M.L. grew up in the atmosphere, with his home being used as a community gathering place, and was no doubt influenced by it. M.L.’s childhood was not especially eventfully. His father was a minister and his mother was a musician. He was the second of three children, and he attended all black schools in a black neighborhood. The neighborhood was not poor, however. Auburn Avenue was an area of banks, insurance companies, builders, jewelers, tailors, doctors, lawyers, and other businesses and services. Even in the face of Atlanta’s segregation, the district thrived. Dr. King never forgot the community spirit he had known as a child, nor did he forget the racial prejudice that was a huge barrier keeping black Atlantans from mingling with whites. M.L. was _______ by the atmosphere in which he grew up.

Xem chi tiết 675 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 Martin Luther King, Jf., is well- known for his work in civil rights and for his many famous speeches, among which is his moving “ I have a dream” speech. But fewer people know much about King’s childhood. M.L., as he was called, was born in 1929 in Atlanta, Georgia, at the home of his maternal grandfather. M.L.’s grandfather purchased their home on Auburn Avenue in 1909, twenty years before M.L was born. His grandfather allowed the house to be used as a meeting place for a number of organizations dedicated to the education and social advancement of blacks. M.L. grew up in the atmosphere, with his home being used as a community gathering place, and was no doubt influenced by it. M.L.’s childhood was not especially eventfully. His father was a minister and his mother was a musician. He was the second of three children, and he attended all black schools in a black neighborhood. The neighborhood was not poor, however. Auburn Avenue was an area of banks, insurance companies, builders, jewelers, tailors, doctors, lawyers, and other businesses and services. Even in the face of Atlanta’s segregation, the district thrived. Dr. King never forgot the community spirit he had known as a child, nor did he forget the racial prejudice that was a huge barrier keeping black Atlantans from mingling with whites. From the passage we can infer that:

Xem chi tiết 1.4 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 Martin Luther King, Jf., is well- known for his work in civil rights and for his many famous speeches, among which is his moving “ I have a dream” speech. But fewer people know much about King’s childhood. M.L., as he was called, was born in 1929 in Atlanta, Georgia, at the home of his maternal grandfather. M.L.’s grandfather purchased their home on Auburn Avenue in 1909, twenty years before M.L was born. His grandfather allowed the house to be used as a meeting place for a number of organizations dedicated to the education and social advancement of blacks. M.L. grew up in the atmosphere, with his home being used as a community gathering place, and was no doubt influenced by it. M.L.’s childhood was not especially eventfully. His father was a minister and his mother was a musician. He was the second of three children, and he attended all black schools in a black neighborhood. The neighborhood was not poor, however. Auburn Avenue was an area of banks, insurance companies, builders, jewelers, tailors, doctors, lawyers, and other businesses and services. Even in the face of Atlanta’s segregation, the district thrived. Dr. King never forgot the community spirit he had known as a child, nor did he forget the racial prejudice that was a huge barrier keeping black Atlantans from mingling with whites. Which of the following statements is NOT true?

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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 Martin Luther King, Jf., is well- known for his work in civil rights and for his many famous speeches, among which is his moving “ I have a dream” speech. But fewer people know much about King’s childhood. M.L., as he was called, was born in 1929 in Atlanta, Georgia, at the home of his maternal grandfather. M.L.’s grandfather purchased their home on Auburn Avenue in 1909, twenty years before M.L was born. His grandfather allowed the house to be used as a meeting place for a number of organizations dedicated to the education and social advancement of blacks. M.L. grew up in the atmosphere, with his home being used as a community gathering place, and was no doubt influenced by it. M.L.’s childhood was not especially eventfully. His father was a minister and his mother was a musician. He was the second of three children, and he attended all black schools in a black neighborhood. The neighborhood was not poor, however. Auburn Avenue was an area of banks, insurance companies, builders, jewelers, tailors, doctors, lawyers, and other businesses and services. Even in the face of Atlanta’s segregation, the district thrived. Dr. King never forgot the community spirit he had known as a child, nor did he forget the racial prejudice that was a huge barrier keeping black Atlantans from mingling with whites. According to the author, M.L. _______. 

Xem chi tiết 313 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 Martin Luther King, Jf., is well- known for his work in civil rights and for his many famous speeches, among which is his moving “ I have a dream” speech. But fewer people know much about King’s childhood. M.L., as he was called, was born in 1929 in Atlanta, Georgia, at the home of his maternal grandfather. M.L.’s grandfather purchased their home on Auburn Avenue in 1909, twenty years before M.L was born. His grandfather allowed the house to be used as a meeting place for a number of organizations dedicated to the education and social advancement of blacks. M.L. grew up in the atmosphere, with his home being used as a community gathering place, and was no doubt influenced by it. M.L.’s childhood was not especially eventfully. His father was a minister and his mother was a musician. He was the second of three children, and he attended all black schools in a black neighborhood. The neighborhood was not poor, however. Auburn Avenue was an area of banks, insurance companies, builders, jewelers, tailors, doctors, lawyers, and other businesses and services. Even in the face of Atlanta’s segregation, the district thrived. Dr. King never forgot the community spirit he had known as a child, nor did he forget the racial prejudice that was a huge barrier keeping black Atlantans from mingling with whites. What is Martin Luthur King well- known for?

Xem chi tiết 514 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 Martin Luther King, Jf., is well- known for his work in civil rights and for his many famous speeches, among which is his moving “ I have a dream” speech. But fewer people know much about King’s childhood. M.L., as he was called, was born in 1929 in Atlanta, Georgia, at the home of his maternal grandfather. M.L.’s grandfather purchased their home on Auburn Avenue in 1909, twenty years before M.L was born. His grandfather allowed the house to be used as a meeting place for a number of organizations dedicated to the education and social advancement of blacks. M.L. grew up in the atmosphere, with his home being used as a community gathering place, and was no doubt influenced by it. M.L.’s childhood was not especially eventfully. His father was a minister and his mother was a musician. He was the second of three children, and he attended all black schools in a black neighborhood. The neighborhood was not poor, however. Auburn Avenue was an area of banks, insurance companies, builders, jewelers, tailors, doctors, lawyers, and other businesses and services. Even in the face of Atlanta’s segregation, the district thrived. Dr. King never forgot the community spirit he had known as a child, nor did he forget the racial prejudice that was a huge barrier keeping black Atlantans from mingling with whites. When was M.L. born?

Xem chi tiết 345 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 Martin Luther King, Jf., is well- known for his work in civil rights and for his many famous speeches, among which is his moving “ I have a dream” speech. But fewer people know much about King’s childhood. M.L., as he was called, was born in 1929 in Atlanta, Georgia, at the home of his maternal grandfather. M.L.’s grandfather purchased their home on Auburn Avenue in 1909, twenty years before M.L was born. His grandfather allowed the house to be used as a meeting place for a number of organizations dedicated to the education and social advancement of blacks. M.L. grew up in the atmosphere, with his home being used as a community gathering place, and was no doubt influenced by it. M.L.’s childhood was not especially eventfully. His father was a minister and his mother was a musician. He was the second of three children, and he attended all black schools in a black neighborhood. The neighborhood was not poor, however. Auburn Avenue was an area of banks, insurance companies, builders, jewelers, tailors, doctors, lawyers, and other businesses and services. Even in the face of Atlanta’s segregation, the district thrived. Dr. King never forgot the community spirit he had known as a child, nor did he forget the racial prejudice that was a huge barrier keeping black Atlantans from mingling with whites. What is the passage mainly about?

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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 for each of the questions. Many ants forage across the countryside in large numbers and undertake mass migrations; these activities proceed because one ant lays a trail on the ground for the others to follow. As a worker ant returns home after finding a source of food, it marks the route Line by intermittently touching its stinger to the ground and depositing a tiny amount of trail pheromone – a mixture of chemicals that delivers diverse messages as the context changes. These trails incorporate no directional information and may be followed by other ants in either direction. Unlike some other messages, such as the one arising from a dead ant, a food trail has to be kept secret from members of other species. It is not surprising then that ant species use a wide variety of compounds as trail pheromones. Ants can be extremely sensitive to these signals. Investigators working with the trail pheromone of the leafcutter ant Atta texana calculated that one milligram of this substance would suffice to lead a column of ants three times around Earth. The vapor of the evaporating pheromone over the trail guides an ant along the way, and the ant detects this signal with receptors in its antennae. A trail pheromone will evaporate to furnish the highest concentration of vapor right over the trail, in what is called a vapor space. In following the trail, the ant moves to the right and left, oscillating from side to side across the line of the trail itself, bringing first one and then the other antenna into the vapor space. As the ant moves to the right, its left antenna arrives in the vapor space. The signal it receives causes it to swing to the left, and the ant then pursues this new course until its right antenna reaches the vapor space. It then swings back to the right, and so weaves back and forth down the trail. According to the passage, the highest amount of pheromone vapor is found

Xem chi tiết 408 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 for each of the questions. Many ants forage across the countryside in large numbers and undertake mass migrations; these activities proceed because one ant lays a trail on the ground for the others to follow. As a worker ant returns home after finding a source of food, it marks the route Line by intermittently touching its stinger to the ground and depositing a tiny amount of trail pheromone – a mixture of chemicals that delivers diverse messages as the context changes. These trails incorporate no directional information and may be followed by other ants in either direction. Unlike some other messages, such as the one arising from a dead ant, a food trail has to be kept secret from members of other species. It is not surprising then that ant species use a wide variety of compounds as trail pheromones. Ants can be extremely sensitive to these signals. Investigators working with the trail pheromone of the leafcutter ant Atta texana calculated that one milligram of this substance would suffice to lead a column of ants three times around Earth. The vapor of the evaporating pheromone over the trail guides an ant along the way, and the ant detects this signal with receptors in its antennae. A trail pheromone will evaporate to furnish the highest concentration of vapor right over the trail, in what is called a vapor space. In following the trail, the ant moves to the right and left, oscillating from side to side across the line of the trail itself, bringing first one and then the other antenna into the vapor space. As the ant moves to the right, its left antenna arrives in the vapor space. The signal it receives causes it to swing to the left, and the ant then pursues this new course until its right antenna reaches the vapor space. It then swings back to the right, and so weaves back and forth down the trail. The word “oscillating“ in line 17 is closest in meaning to

Xem chi tiết 280 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 for each of the questions. Many ants forage across the countryside in large numbers and undertake mass migrations; these activities proceed because one ant lays a trail on the ground for the others to follow. As a worker ant returns home after finding a source of food, it marks the route Line by intermittently touching its stinger to the ground and depositing a tiny amount of trail pheromone – a mixture of chemicals that delivers diverse messages as the context changes. These trails incorporate no directional information and may be followed by other ants in either direction. Unlike some other messages, such as the one arising from a dead ant, a food trail has to be kept secret from members of other species. It is not surprising then that ant species use a wide variety of compounds as trail pheromones. Ants can be extremely sensitive to these signals. Investigators working with the trail pheromone of the leafcutter ant Atta texana calculated that one milligram of this substance would suffice to lead a column of ants three times around Earth. The vapor of the evaporating pheromone over the trail guides an ant along the way, and the ant detects this signal with receptors in its antennae. A trail pheromone will evaporate to furnish the highest concentration of vapor right over the trail, in what is called a vapor space. In following the trail, the ant moves to the right and left, oscillating from side to side across the line of the trail itself, bringing first one and then the other antenna into the vapor space. As the ant moves to the right, its left antenna arrives in the vapor space. The signal it receives causes it to swing to the left, and the ant then pursues this new course until its right antenna reaches the vapor space. It then swings back to the right, and so weaves back and forth down the trail. According to the passage, how are ants guided by trail pheromones?

Xem chi tiết 772 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 for each of the questions. Many ants forage across the countryside in large numbers and undertake mass migrations; these activities proceed because one ant lays a trail on the ground for the others to follow. As a worker ant returns home after finding a source of food, it marks the route Line by intermittently touching its stinger to the ground and depositing a tiny amount of trail pheromone – a mixture of chemicals that delivers diverse messages as the context changes. These trails incorporate no directional information and may be followed by other ants in either direction. Unlike some other messages, such as the one arising from a dead ant, a food trail has to be kept secret from members of other species. It is not surprising then that ant species use a wide variety of compounds as trail pheromones. Ants can be extremely sensitive to these signals. Investigators working with the trail pheromone of the leafcutter ant Atta texana calculated that one milligram of this substance would suffice to lead a column of ants three times around Earth. The vapor of the evaporating pheromone over the trail guides an ant along the way, and the ant detects this signal with receptors in its antennae. A trail pheromone will evaporate to furnish the highest concentration of vapor right over the trail, in what is called a vapor space. In following the trail, the ant moves to the right and left, oscillating from side to side across the line of the trail itself, bringing first one and then the other antenna into the vapor space. As the ant moves to the right, its left antenna arrives in the vapor space. The signal it receives causes it to swing to the left, and the ant then pursues this new course until its right antenna reaches the vapor space. It then swings back to the right, and so weaves back and forth down the trail. The author mentions the trail pheromone of the leafcutter ant in line 11 to point out

Xem chi tiết 404 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 for each of the questions. Many ants forage across the countryside in large numbers and undertake mass migrations; these activities proceed because one ant lays a trail on the ground for the others to follow. As a worker ant returns home after finding a source of food, it marks the route Line by intermittently touching its stinger to the ground and depositing a tiny amount of trail pheromone – a mixture of chemicals that delivers diverse messages as the context changes. These trails incorporate no directional information and may be followed by other ants in either direction. Unlike some other messages, such as the one arising from a dead ant, a food trail has to be kept secret from members of other species. It is not surprising then that ant species use a wide variety of compounds as trail pheromones. Ants can be extremely sensitive to these signals. Investigators working with the trail pheromone of the leafcutter ant Atta texana calculated that one milligram of this substance would suffice to lead a column of ants three times around Earth. The vapor of the evaporating pheromone over the trail guides an ant along the way, and the ant detects this signal with receptors in its antennae. A trail pheromone will evaporate to furnish the highest concentration of vapor right over the trail, in what is called a vapor space. In following the trail, the ant moves to the right and left, oscillating from side to side across the line of the trail itself, bringing first one and then the other antenna into the vapor space. As the ant moves to the right, its left antenna arrives in the vapor space. The signal it receives causes it to swing to the left, and the ant then pursues this new course until its right antenna reaches the vapor space. It then swings back to the right, and so weaves back and forth down the trail. According to the passage, why do ants use different compounds as trail pheromones?

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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 for each of the questions. Many ants forage across the countryside in large numbers and undertake mass migrations; these activities proceed because one ant lays a trail on the ground for the others to follow. As a worker ant returns home after finding a source of food, it marks the route Line by intermittently touching its stinger to the ground and depositing a tiny amount of trail pheromone – a mixture of chemicals that delivers diverse messages as the context changes. These trails incorporate no directional information and may be followed by other ants in either direction. Unlike some other messages, such as the one arising from a dead ant, a food trail has to be kept secret from members of other species. It is not surprising then that ant species use a wide variety of compounds as trail pheromones. Ants can be extremely sensitive to these signals. Investigators working with the trail pheromone of the leafcutter ant Atta texana calculated that one milligram of this substance would suffice to lead a column of ants three times around Earth. The vapor of the evaporating pheromone over the trail guides an ant along the way, and the ant detects this signal with receptors in its antennae. A trail pheromone will evaporate to furnish the highest concentration of vapor right over the trail, in what is called a vapor space. In following the trail, the ant moves to the right and left, oscillating from side to side across the line of the trail itself, bringing first one and then the other antenna into the vapor space. As the ant moves to the right, its left antenna arrives in the vapor space. The signal it receives causes it to swing to the left, and the ant then pursues this new course until its right antenna reaches the vapor space. It then swings back to the right, and so weaves back and forth down the trail. The phrase “the one” in line 8 refers to a single.

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