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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 43 to 50.There are many theories of aging, but virtually all fall into the category of being hypotheses with a minimum of supporting evidence. One viewpoint is that aging occurs as the body's organ systems become less efficient. Thus failures in the immune system, hormonal system, and nervous system could all produce characteristics that we associate with aging. Following a different vein, many current researchers are looking for evidence at the cellular and sub cellular level.It has been shown that cells such as human fibroblasts (generalized tissue cells) grown in culture divide only a limited number of times and then die. (Only cancer cells seem immortal in this respect). Fibroblast cells from an embryo divide more times than those taken from an adult. Thus some researchers believe that aging occurs at the cellular level and is part of the cell's genetic makeup. Any event that disturbs the cell's genetic machinery such as mutation, damaging chemicals in the cell's environment, or loss of genetic material, could cause cells to lose their ability to divide and thus bring on aging. Other theories of aging look at different processes. Chronological aging refers to the passage of time since birth and is usually measured in years. While chronological age can be useful in estimating the average status of a large group of people, it is a poor indicator of an individual person's status because there is a tremendous amount of variation from one individual to the next in regard to the rate at which biological age changes occur. For example, on the average, aging results in people losing much of their ability to perform strenuous activities, yet some elderly individuals are excellent marathon runners.Another type of aging is cosmetic aging, which consists of changes in outward appearance with advancing age. This includes changes in the body and changes in other aspects of a person's appearance, such as the style of hair and clothing, the type of eyeglasses, and the use of a hearing aid. Like chronological aging, it is frequently used to estimate the degree to which other types of aging have occurred. However, it is an inaccurate indicator for either purpose because of variation among individuals and because a person's appearance is affected by many factors that are not part of aging, including illness, poor nutrition, and exposure to sunlightThe word “strenuous” in paragraph 3 is closest in meaning to_____________.
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 43 to 50.There are many theories of aging, but virtually all fall into the category of being hypotheses with a minimum of supporting evidence. One viewpoint is that aging occurs as the body's organ systems become less efficient. Thus failures in the immune system, hormonal system, and nervous system could all produce characteristics that we associate with aging. Following a different vein, many current researchers are looking for evidence at the cellular and sub cellular level.It has been shown that cells such as human fibroblasts (generalized tissue cells) grown in culture divide only a limited number of times and then die. (Only cancer cells seem immortal in this respect). Fibroblast cells from an embryo divide more times than those taken from an adult. Thus some researchers believe that aging occurs at the cellular level and is part of the cell's genetic makeup. Any event that disturbs the cell's genetic machinery such as mutation, damaging chemicals in the cell's environment, or loss of genetic material, could cause cells to lose their ability to divide and thus bring on aging. Other theories of aging look at different processes. Chronological aging refers to the passage of time since birth and is usually measured in years. While chronological age can be useful in estimating the average status of a large group of people, it is a poor indicator of an individual person's status because there is a tremendous amount of variation from one individual to the next in regard to the rate at which biological age changes occur. For example, on the average, aging results in people losing much of their ability to perform strenuous activities, yet some elderly individuals are excellent marathon runners.Another type of aging is cosmetic aging, which consists of changes in outward appearance with advancing age. This includes changes in the body and changes in other aspects of a person's appearance, such as the style of hair and clothing, the type of eyeglasses, and the use of a hearing aid. Like chronological aging, it is frequently used to estimate the degree to which other types of aging have occurred. However, it is an inaccurate indicator for either purpose because of variation among individuals and because a person's appearance is affected by many factors that are not part of aging, including illness, poor nutrition, and exposure to sunlightThe phrase “an embryo” in paragraph 2 is closest in meaning to_____________
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 43 to 50.There are many theories of aging, but virtually all fall into the category of being hypotheses with a minimum of supporting evidence. One viewpoint is that aging occurs as the body's organ systems become less efficient. Thus failures in the immune system, hormonal system, and nervous system could all produce characteristics that we associate with aging. Following a different vein, many current researchers are looking for evidence at the cellular and sub cellular level.It has been shown that cells such as human fibroblasts (generalized tissue cells) grown in culture divide only a limited number of times and then die. (Only cancer cells seem immortal in this respect). Fibroblast cells from an embryo divide more times than those taken from an adult. Thus some researchers believe that aging occurs at the cellular level and is part of the cell's genetic makeup. Any event that disturbs the cell's genetic machinery such as mutation, damaging chemicals in the cell's environment, or loss of genetic material, could cause cells to lose their ability to divide and thus bring on aging. Other theories of aging look at different processes. Chronological aging refers to the passage of time since birth and is usually measured in years. While chronological age can be useful in estimating the average status of a large group of people, it is a poor indicator of an individual person's status because there is a tremendous amount of variation from one individual to the next in regard to the rate at which biological age changes occur. For example, on the average, aging results in people losing much of their ability to perform strenuous activities, yet some elderly individuals are excellent marathon runners.Another type of aging is cosmetic aging, which consists of changes in outward appearance with advancing age. This includes changes in the body and changes in other aspects of a person's appearance, such as the style of hair and clothing, the type of eyeglasses, and the use of a hearing aid. Like chronological aging, it is frequently used to estimate the degree to which other types of aging have occurred. However, it is an inaccurate indicator for either purpose because of variation among individuals and because a person's appearance is affected by many factors that are not part of aging, including illness, poor nutrition, and exposure to sunlightThe author points out that cancer cells_____________
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 43 to 50.There are many theories of aging, but virtually all fall into the category of being hypotheses with a minimum of supporting evidence. One viewpoint is that aging occurs as the body's organ systems become less efficient. Thus failures in the immune system, hormonal system, and nervous system could all produce characteristics that we associate with aging. Following a different vein, many current researchers are looking for evidence at the cellular and sub cellular level.It has been shown that cells such as human fibroblasts (generalized tissue cells) grown in culture divide only a limited number of times and then die. (Only cancer cells seem immortal in this respect). Fibroblast cells from an embryo divide more times than those taken from an adult. Thus some researchers believe that aging occurs at the cellular level and is part of the cell's genetic makeup. Any event that disturbs the cell's genetic machinery such as mutation, damaging chemicals in the cell's environment, or loss of genetic material, could cause cells to lose their ability to divide and thus bring on aging. Other theories of aging look at different processes. Chronological aging refers to the passage of time since birth and is usually measured in years. While chronological age can be useful in estimating the average status of a large group of people, it is a poor indicator of an individual person's status because there is a tremendous amount of variation from one individual to the next in regard to the rate at which biological age changes occur. For example, on the average, aging results in people losing much of their ability to perform strenuous activities, yet some elderly individuals are excellent marathon runners.Another type of aging is cosmetic aging, which consists of changes in outward appearance with advancing age. This includes changes in the body and changes in other aspects of a person's appearance, such as the style of hair and clothing, the type of eyeglasses, and the use of a hearing aid. Like chronological aging, it is frequently used to estimate the degree to which other types of aging have occurred. However, it is an inaccurate indicator for either purpose because of variation among individuals and because a person's appearance is affected by many factors that are not part of aging, including illness, poor nutrition, and exposure to sunlightWhat is the best title for this passage?
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 38 to 42.Tsunami is a Japanese word which means harbour wave and is used as the scientific term for seismic sea wave generated by an undersea earthquake or possibly an undersea landside or volcanic eruption, when the ocean floor is tilted or offset during an earthquake, a set of waves is created similar to the concentric waves generated by an object dropped into the water. Most tsunamis originate along the Ring of Fire, a zone of volcanoes and seismic activity, 32,500 km long that encircles the Pacific Ocean. Since 1819, about 40 tsunamis have struck the Hawaiian Islands.A tsunami can have wavelengths, or widths, of 100 to 200 km, and may travel hundreds of kilometers across the deep ocean, reaching speeds of about 725 to 800 kilometres an hour. Upon entering shallow coastal waters, the wave, which may have been only about half a metre high out at sea, suddenly grows rapidly. When the wave reaches the shore, it maybe 15 m high or more. Tsunamis have tremendous energy because of the great volume of water affected. They are capable of obliterating coastal settlements.Tsunamis should nót be confused with storm surges, which are domes of water that rise underneath hurricanes or cyclones and cause extensive coastal flooding when the storms reach land. Storm surges are particularly devastating if they occur at high tide. A cyclone and accompanying storm surge skilled an estimated 500,000 people in Bangladesh in 1970. The tsunami which struck south and southeast Asia in late 2004 killed over 200 thousand peoplewhat is the passage mainly about?
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 38 to 42.Tsunami is a Japanese word which means harbour wave and is used as the scientific term for seismic sea wave generated by an undersea earthquake or possibly an undersea landside or volcanic eruption, when the ocean floor is tilted or offset during an earthquake, a set of waves is created similar to the concentric waves generated by an object dropped into the water. Most tsunamis originate along the Ring of Fire, a zone of volcanoes and seismic activity, 32,500 km long that encircles the Pacific Ocean. Since 1819, about 40 tsunamis have struck the Hawaiian Islands.A tsunami can have wavelengths, or widths, of 100 to 200 km, and may travel hundreds of kilometers across the deep ocean, reaching speeds of about 725 to 800 kilometres an hour. Upon entering shallow coastal waters, the wave, which may have been only about half a metre high out at sea, suddenly grows rapidly. When the wave reaches the shore, it maybe 15 m high or more. Tsunamis have tremendous energy because of the great volume of water affected. They are capable of obliterating coastal settlements.Tsunamis should nót be confused with storm surges, which are domes of water that rise underneath hurricanes or cyclones and cause extensive coastal flooding when the storms reach land. Storm surges are particularly devastating if they occur at high tide. A cyclone and accompanying storm surge skilled an estimated 500,000 people in Bangladesh in 1970. The tsunami which struck south and southeast Asia in late 2004 killed over 200 thousand peopleWhich of the following is NOT true?
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 38 to 42.Tsunami is a Japanese word which means harbour wave and is used as the scientific term for seismic sea wave generated by an undersea earthquake or possibly an undersea landside or volcanic eruption, when the ocean floor is tilted or offset during an earthquake, a set of waves is created similar to the concentric waves generated by an object dropped into the water. Most tsunamis originate along the Ring of Fire, a zone of volcanoes and seismic activity, 32,500 km long that encircles the Pacific Ocean. Since 1819, about 40 tsunamis have struck the Hawaiian Islands.A tsunami can have wavelengths, or widths, of 100 to 200 km, and may travel hundreds of kilometers across the deep ocean, reaching speeds of about 725 to 800 kilometres an hour. Upon entering shallow coastal waters, the wave, which may have been only about half a metre high out at sea, suddenly grows rapidly. When the wave reaches the shore, it maybe 15 m high or more. Tsunamis have tremendous energy because of the great volume of water affected. They are capable of obliterating coastal settlements.Tsunamis should nót be confused with storm surges, which are domes of water that rise underneath hurricanes or cyclones and cause extensive coastal flooding when the storms reach land. Storm surges are particularly devastating if they occur at high tide. A cyclone and accompanying storm surge skilled an estimated 500,000 people in Bangladesh in 1970. The tsunami which struck south and southeast Asia in late 2004 killed over 200 thousand people.How are tsunami capable of obliterating coastal settlements?
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 38 to 42.Tsunami is a Japanese word which means harbour wave and is used as the scientific term for seismic sea wave generated by an undersea earthquake or possibly an undersea landside or volcanic eruption, when the ocean floor is tilted or offset during an earthquake, a set of waves is created similar to the concentric waves generated by an object dropped into the water. Most tsunamis originate along the Ring of Fire, a zone of volcanoes and seismic activity, 32,500 km long that encircles the Pacific Ocean. Since 1819, about 40 tsunamis have struck the Hawaiian Islands.A tsunami can have wavelengths, or widths, of 100 to 200 km, and may travel hundreds of kilometers across the deep ocean, reaching speeds of about 725 to 800 kilometres an hour. Upon entering shallow coastal waters, the wave, which may have been only about half a metre high out at sea, suddenly grows rapidly. When the wave reaches the shore, it maybe 15 m high or more. Tsunamis have tremendous energy because of the great volume of water affected. They are capable of obliterating coastal settlements.Tsunamis should nót be confused with storm surges, which are domes of water that rise underneath hurricanes or cyclones and cause extensive coastal flooding when the storms reach land. Storm surges are particularly devastating if they occur at high tide. A cyclone and accompanying storm surge skilled an estimated 500,000 people in Bangladesh in 1970. The tsunami which struck south and southeast Asia in late 2004 killed over 200 thousand peoplewhat is the greatest speed of tsunami travelling across the deep ocean?
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 38 to 42.Tsunami is a Japanese word which means harbour wave and is used as the scientific term for seismic sea wave generated by an undersea earthquake or possibly an undersea landside or volcanic eruption, when the ocean floor is tilted or offset during an earthquake, a set of waves is created similar to the concentric waves generated by an object dropped into the water. Most tsunamis originate along the Ring of Fire, a zone of volcanoes and seismic activity, 32,500 km long that encircles the Pacific Ocean. Since 1819, about 40 tsunamis have struck the Hawaiian Islands.A tsunami can have wavelengths, or widths, of 100 to 200 km, and may travel hundreds of kilometers across the deep ocean, reaching speeds of about 725 to 800 kilometres an hour. Upon entering shallow coastal waters, the wave, which may have been only about half a metre high out at sea, suddenly grows rapidly. When the wave reaches the shore, it maybe 15 m high or more. Tsunamis have tremendous energy because of the great volume of water affected. They are capable of obliterating coastal settlements.Tsunamis should nót be confused with storm surges, which are domes of water that rise underneath hurricanes or cyclones and cause extensive coastal flooding when the storms reach land. Storm surges are particularly devastating if they occur at high tide. A cyclone and accompanying storm surge skilled an estimated 500,000 people in Bangladesh in 1970. The tsunami which struck south and southeast Asia in late 2004 killed over 200 thousand people.What does the word “concentric” in paragraph 1 mean?
Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word for each of the blanks from 33 to 37.The story of gold is an adventure involving kings, queens, pirates, explorers, conquerors, andthe native people they conquered. Throughout history, gold has (33) _____________a magic spell overthose it touched. Gold is beautiful and rare; a soft shiny metal that can be moulded into many shapes. It has been used for money, jewelry, and to decorate special buildings such as palaces and places of worship. (34) _____________the precious metal was discovered, prospectors rushed to mine it, starting new cities and countries as they went. Gold and the people who love it have helped shape the world we live in today. Gold is one of many elements, or substances that cannot be changed by normal chemical means, that are found in the Earth's crust. Gold has a warm, sunny colour and (35) _____________it does not react with air, water, and most chemicals, its shine never fades. In its natural (36) _____________, gold is soft and easily shaped, when heated to 1,062 Celsius it melts and can be poured (37) _____________moulds to form coins, gold bars, and other objects. Stories have been told, movies made and legends born about the discovery of the world's great gold deposits. It is a saga of dreams, greed, ambition and exploration.
Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word for each of the blanks from 33 to 37.The story of gold is an adventure involving kings, queens, pirates, explorers, conquerors, andthe native people they conquered. Throughout history, gold has (33) _____________a magic spell overthose it touched. Gold is beautiful and rare; a soft shiny metal that can be moulded into many shapes. It has been used for money, jewelry, and to decorate special buildings such as palaces and places of worship. (34) _____________the precious metal was discovered, prospectors rushed to mine it, starting new cities and countries as they went. Gold and the people who love it have helped shape the world we live in today. Gold is one of many elements, or substances that cannot be changed by normal chemical means, that are found in the Earth's crust. Gold has a warm, sunny colour and (35) _____________it does not react with air, water, and most chemicals, its shine never fades. In its natural (36) _____________, gold is soft and easily shaped, when heated to 1,062 Celsius it melts and can be poured (37) _____________moulds to form coins, gold bars, and other objects. Stories have been told, movies made and legends born about the discovery of the world's great gold deposits. It is a saga of dreams, greed, ambition and exploration.
Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word for each of the blanks from 33 to 37.The story of gold is an adventure involving kings, queens, pirates, explorers, conquerors, andthe native people they conquered. Throughout history, gold has (33) _____________a magic spell overthose it touched. Gold is beautiful and rare; a soft shiny metal that can be moulded into many shapes. It has been used for money, jewelry, and to decorate special buildings such as palaces and places of worship. (34) _____________the precious metal was discovered, prospectors rushed to mine it, starting new cities and countries as they went. Gold and the people who love it have helped shape the world we live in today. Gold is one of many elements, or substances that cannot be changed by normal chemical means, that are found in the Earth's crust. Gold has a warm, sunny colour and (35) _____________it does not react with air, water, and most chemicals, its shine never fades. In its natural (36) _____________, gold is soft and easily shaped, when heated to 1,062 Celsius it melts and can be poured (37) _____________moulds to form coins, gold bars, and other objects. Stories have been told, movies made and legends born about the discovery of the world's great gold deposits. It is a saga of dreams, greed, ambition and exploration.
Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word for each of the blanks from 33 to 37.The story of gold is an adventure involving kings, queens, pirates, explorers, conquerors, andthe native people they conquered. Throughout history, gold has (33) _____________a magic spell overthose it touched. Gold is beautiful and rare; a soft shiny metal that can be moulded into many shapes. It has been used for money, jewelry, and to decorate special buildings such as palaces and places of worship. (34) _____________the precious metal was discovered, prospectors rushed to mine it, starting new cities and countries as they went. Gold and the people who love it have helped shape the world we live in today. Gold is one of many elements, or substances that cannot be changed by normal chemical means, that are found in the Earth's crust. Gold has a warm, sunny colour and (35) _____________it does not react with air, water, and most chemicals, its shine never fades. In its natural (36) _____________, gold is soft and easily shaped, when heated to 1,062 Celsius it melts and can be poured (37) _____________moulds to form coins, gold bars, and other objects. Stories have been told, movies made and legends born about the discovery of the world's great gold deposits. It is a saga of dreams, greed, ambition and exploration.
Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word for each of the blanks from 33 to 37.The story of gold is an adventure involving kings, queens, pirates, explorers, conquerors, andthe native people they conquered. Throughout history, gold has (33) _____________a magic spell overthose it touched. Gold is beautiful and rare; a soft shiny metal that can be moulded into many shapes. It has been used for money, jewelry, and to decorate special buildings such as palaces and places of worship. (34) _____________the precious metal was discovered, prospectors rushed to mine it, starting new cities and countries as they went. Gold and the people who love it have helped shape the world we live in today. Gold is one of many elements, or substances that cannot be changed by normal chemical means, that are found in the Earth's crust. Gold has a warm, sunny colour and (35) _____________it does not react with air, water, and most chemicals, its shine never fades. In its natural (36) _____________, gold is soft and easily shaped, when heated to 1,062 Celsius it melts and can be poured (37) _____________moulds to form coins, gold bars, and other objects. Stories have been told, movies made and legends born about the discovery of the world's great gold deposits. It is a saga of dreams, greed, ambition and exploration.
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 43 to 50.The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen.Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in relatively young ones, in interstellar gas, and in the distant objects known as quasars. Helium nuclei have also been found to be constituents of cosmic rays that fall on the earth (cosmic rays are not really a form of radiation; they consist of rapidly moving particles of numerous different kinds). It doesn’t seem to make very much difference where the helium is found. Its relative abundance never seems to vary much. In some places, there may be slightly more of it; in others, slightly less, but the ratio of helium to hydrogen nuclei always remains about the same.Helium is created in stars. In fact, nuclear reactions that convert hydrogen to helium are responsible for most of the energy that stars produce. However, the amount of helium that could have been produced in this manner can be calculated, and it turns out to be no more than a few percent. The universe has not existed long enough for this figure to be significantly greater. Consequently, if the universe is somewhat more than 25 percent helium now, then it must have been about 25 percent helium at a time near the beginning.However, when the universe was less than one minute old, no helium could have existed. Calculations indicate that before this time temperatures were too high and particles of matter were moving around much too rapidly. It was only after the one- minute point that helium could exist. By this time, the universe had cooled so sufficiently that neutrons and protons could stick together. But the nuclear reactions that led to the formations of helium went on for only relatively short time. By the time the universe was a few minutes old, helium production had effectively ceasedMost of the helium in the universe was formed____________
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 43 to 50.The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen.Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in relatively young ones, in interstellar gas, and in the distant objects known as quasars. Helium nuclei have also been found to be constituents of cosmic rays that fall on the earth (cosmic rays are not really a form of radiation; they consist of rapidly moving particles of numerous different kinds). It doesn’t seem to make very much difference where the helium is found. Its relative abundance never seems to vary much. In some places, there may be slightly more of it; in others, slightly less, but the ratio of helium to hydrogen nuclei always remains about the same.Helium is created in stars. In fact, nuclear reactions that convert hydrogen to helium are responsible for most of the energy that stars produce. However, the amount of helium that could have been produced in this manner can be calculated, and it turns out to be no more than a few percent. The universe has not existed long enough for this figure to be significantly greater. Consequently, if the universe is somewhat more than 25 percent helium now, then it must have been about 25 percent helium at a time near the beginning.However, when the universe was less than one minute old, no helium could have existed. Calculations indicate that before this time temperatures were too high and particles of matter were moving around much too rapidly. It was only after the one- minute point that helium could exist. By this time, the universe had cooled so sufficiently that neutrons and protons could stick together. But the nuclear reactions that led to the formations of helium went on for only relatively short time. By the time the universe was a few minutes old, helium production had effectively ceasedThe creation of helium within stars____________.
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 43 to 50.The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen.Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in relatively young ones, in interstellar gas, and in the distant objects known as quasars. Helium nuclei have also been found to be constituents of cosmic rays that fall on the earth (cosmic rays are not really a form of radiation; they consist of rapidly moving particles of numerous different kinds). It doesn’t seem to make very much difference where the helium is found. Its relative abundance never seems to vary much. In some places, there may be slightly more of it; in others, slightly less, but the ratio of helium to hydrogen nuclei always remains about the same.Helium is created in stars. In fact, nuclear reactions that convert hydrogen to helium are responsible for most of the energy that stars produce. However, the amount of helium that could have been produced in this manner can be calculated, and it turns out to be no more than a few percent. The universe has not existed long enough for this figure to be significantly greater. Consequently, if the universe is somewhat more than 25 percent helium now, then it must have been about 25 percent helium at a time near the beginning.However, when the universe was less than one minute old, no helium could have existed. Calculations indicate that before this time temperatures were too high and particles of matter were moving around much too rapidly. It was only after the one- minute point that helium could exist. By this time, the universe had cooled so sufficiently that neutrons and protons could stick together. But the nuclear reactions that led to the formations of helium went on for only relatively short time. By the time the universe was a few minutes old, helium production had effectively ceasedThe word “vary” is closest in meaning to____________.
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 43 to 50.The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen.Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in relatively young ones, in interstellar gas, and in the distant objects known as quasars. Helium nuclei have also been found to be constituents of cosmic rays that fall on the earth (cosmic rays are not really a form of radiation; they consist of rapidly moving particles of numerous different kinds). It doesn’t seem to make very much difference where the helium is found. Its relative abundance never seems to vary much. In some places, there may be slightly more of it; in others, slightly less, but the ratio of helium to hydrogen nuclei always remains about the same.Helium is created in stars. In fact, nuclear reactions that convert hydrogen to helium are responsible for most of the energy that stars produce. However, the amount of helium that could have been produced in this manner can be calculated, and it turns out to be no more than a few percent. The universe has not existed long enough for this figure to be significantly greater. Consequently, if the universe is somewhat more than 25 percent helium now, then it must have been about 25 percent helium at a time near the beginning.However, when the universe was less than one minute old, no helium could have existed. Calculations indicate that before this time temperatures were too high and particles of matter were moving around much too rapidly. It was only after the one- minute point that helium could exist. By this time, the universe had cooled so sufficiently that neutrons and protons could stick together. But the nuclear reactions that led to the formations of helium went on for only relatively short time. By the time the universe was a few minutes old, helium production had effectively ceasedThe word “they” refers to____________
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 43 to 50.The elements other than hydrogen and helium exist in such small quantities that it is accurate to say that the universe is somewhat more than 25 percent helium by weight and somewhat less than 75 percent hydrogen.Astronomers have measured the abundance of helium throughout our galaxy and in other galaxies as well. Helium has been found in old stars, in relatively young ones, in interstellar gas, and in the distant objects known as quasars. Helium nuclei have also been found to be constituents of cosmic rays that fall on the earth (cosmic rays are not really a form of radiation; they consist of rapidly moving particles of numerous different kinds). It doesn’t seem to make very much difference where the helium is found. Its relative abundance never seems to vary much. In some places, there may be slightly more of it; in others, slightly less, but the ratio of helium to hydrogen nuclei always remains about the same.Helium is created in stars. In fact, nuclear reactions that convert hydrogen to helium are responsible for most of the energy that stars produce. However, the amount of helium that could have been produced in this manner can be calculated, and it turns out to be no more than a few percent. The universe has not existed long enough for this figure to be significantly greater. Consequently, if the universe is somewhat more than 25 percent helium now, then it must have been about 25 percent helium at a time near the beginning.However, when the universe was less than one minute old, no helium could have existed. Calculations indicate that before this time temperatures were too high and particles of matter were moving around much too rapidly. It was only after the one- minute point that helium could exist. By this time, the universe had cooled so sufficiently that neutrons and protons could stick together. But the nuclear reactions that led to the formations of helium went on for only relatively short time. By the time the universe was a few minutes old, helium production had effectively ceasedWhy does the author mention “cosmic rays”?