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Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 36 to 42. The concept of obtaining fresh water from iceberg that is towed to populated areas and arid regions of the world was once treated as a joke more appropriate to cartoons than real life. But now it is being considered quite seriously by many nations, especially since scientists have warned that the human race will outgrow its fresh water supply faster than it runs out of food. Glaciers are a possible source of fresh water that has been overlooked until recently. (A) Three-quarters of the Earth's fresh water supply is still tied up in glacial ice, a reservoir of untapped fresh water so immense that it could sustain all the rivers of the world for 1,000 years. Floating on the oceans every year are 7,659 trillion metric tons of ice encased in 10,000 icebergs that break away from the polar ice caps, more than ninety percent of them from Antarctica. (B) Huge glaciers that stretch over the shallow continental shelf give birth to icebergs throughout the year. Icebergs are not like sea ice, which is formed when the sea itself freezes; rather, they are formed entirely on land, breaking off when glaciers spread over the sea. As they drift away from the polar region, icebergs sometimes move mysteriously in a direction opposite to the wind, pulled by subsurface currents. Because they melt more slowly than smaller pieces of ice, icebergs have been known to drift as far north as 35 degrees south of the equator in the Atlantic Ocean. (C) The difficulty arises in other technical matters, such as the prevention of rapid melting in warmer climates and the funneling of fresh water to shore in great volume. But even if the icebergs lost half of their volume in towing, the water they could provide would be far cheaper than that produced by desalination, or removing salt from water. (D) Question 38: The word “it” in the first paragraph refers to _________.
Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 36 to 42. The concept of obtaining fresh water from iceberg that is towed to populated areas and arid regions of the world was once treated as a joke more appropriate to cartoons than real life. But now it is being considered quite seriously by many nations, especially since scientists have warned that the human race will outgrow its fresh water supply faster than it runs out of food. Glaciers are a possible source of fresh water that has been overlooked until recently. (A) Three-quarters of the Earth's fresh water supply is still tied up in glacial ice, a reservoir of untapped fresh water so immense that it could sustain all the rivers of the world for 1,000 years. Floating on the oceans every year are 7,659 trillion metric tons of ice encased in 10,000 icebergs that break away from the polar ice caps, more than ninety percent of them from Antarctica. (B) Huge glaciers that stretch over the shallow continental shelf give birth to icebergs throughout the year. Icebergs are not like sea ice, which is formed when the sea itself freezes; rather, they are formed entirely on land, breaking off when glaciers spread over the sea. As they drift away from the polar region, icebergs sometimes move mysteriously in a direction opposite to the wind, pulled by subsurface currents. Because they melt more slowly than smaller pieces of ice, icebergs have been known to drift as far north as 35 degrees south of the equator in the Atlantic Ocean. (C) The difficulty arises in other technical matters, such as the prevention of rapid melting in warmer climates and the funneling of fresh water to shore in great volume. But even if the icebergs lost half of their volume in towing, the water they could provide would be far cheaper than that produced by desalination, or removing salt from water. (D) Question 37: The word “arid” in the first paragraph is closest in meaning to ________.
Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions from 36 to 42. The concept of obtaining fresh water from iceberg that is towed to populated areas and arid regions of the world was once treated as a joke more appropriate to cartoons than real life. But now it is being considered quite seriously by many nations, especially since scientists have warned that the human race will outgrow its fresh water supply faster than it runs out of food. Glaciers are a possible source of fresh water that has been overlooked until recently. (A) Three-quarters of the Earth's fresh water supply is still tied up in glacial ice, a reservoir of untapped fresh water so immense that it could sustain all the rivers of the world for 1,000 years. Floating on the oceans every year are 7,659 trillion metric tons of ice encased in 10,000 icebergs that break away from the polar ice caps, more than ninety percent of them from Antarctica. (B) Huge glaciers that stretch over the shallow continental shelf give birth to icebergs throughout the year. Icebergs are not like sea ice, which is formed when the sea itself freezes; rather, they are formed entirely on land, breaking off when glaciers spread over the sea. As they drift away from the polar region, icebergs sometimes move mysteriously in a direction opposite to the wind, pulled by subsurface currents. Because they melt more slowly than smaller pieces of ice, icebergs have been known to drift as far north as 35 degrees south of the equator in the Atlantic Ocean. (C) The difficulty arises in other technical matters, such as the prevention of rapid melting in warmer climates and the funneling of fresh water to shore in great volume. But even if the icebergs lost half of their volume in towing, the water they could provide would be far cheaper than that produced by desalination, or removing salt from water. (D) Question 36: What is the main topic of the 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 28 to 34.         It is estimated that over 99 percent of all species that ever existed have become extinct. What causes extinction? When a species is no longer adapted to a changed environment, it may perish. The exact causes of a species' death vary from situation to situation. Rapid ecological change may render an environment hostile to a species. For example, temperatures may change and a species may not be able to adapt. Food Resources may be affected by environmental changes, which will then cause problems for a species requiring these resources. Other species may become better adapted to an environment, resulting in competition and, ultimately, in the death of a species.         The fossil record reveals that extinction has occurred throughout the history of Earth. Recent analyses have also revealed that on some occasions many species became extinct at the same time - a mass extinction. One of the best-known examples of mass extinction occurred 65 million years ago with the demise of dinosaurs and many other forms of life. Perhaps the largest mass extinction was the one that occurred 225 million years ago. When approximately 95 percent of all species died, mass extinctions can be caused by a relatively rapid change in the environment and can be worsened by the close interrelationship of many species. If, for example, something were to happen to destroy much of the plankton in the oceans, then the oxygen content of Earth would drop, affection even organisms not living in the oceans. Such a change would probably lead to a mass extinction.         One interesting, and controversial, finding is that extinctions during the past 250 million years have tended to be more intense every 26 million years. This periodic extinction might be due to intersection of the Earth’s orbit with a cloud of comets, but this theory is purely speculative. Some researchers have also speculated that extinction may often be random. That is, certain species may be eliminated and others may survive for no particular reason. A species’ survival may have nothing to do with its ability or inability to adapt. If so, some of evolutionary history may reflect a sequence of essentially random events. Which of the following can be inferred from the theory of periodic extinction mentioned in paragraph 3?
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.         A considerable body of research has demonstrated a correlation between birth order and aspects such as temperament and behavior, and some psychologists believe that birth order significantly affects the development of personality. Psychologist Alfred Adler was a pioneer in the study of the relationship between birth order and personality. A key point in his research and in the hypothesis that he developed based on it was that it was not the actual numerical birth position that affected personality; instead, it was the similar responses in large numbers of families to children in specific birth order positions that had an effect. For example, first - borns, who have their parents to themselves initially and do not have to deal with siblings in the first part of their lives, tend to have their first socialization experiences with adults and therefore tend to find the process of peer socialization more difficult. In contrast, later-born children have to deal with siblings from the first moment of their lives and therefore tend to have stronger socialization skills.         Numerous studies since Adler’s have been conducted on the effect of birth order and personality. These studies have tended to classify birth order types into four different categories: first-born, second-born and/or middle, last, and only child.         Studies have consistently shown that first-bom children tend to exhibit similar, positive and negative personality traits. First-borns have consistently been linked with academic achievement in various studies; in one study, the number of National Merit scholarship winners who are first­ - borns was found to be equal to the number of second - and third-borns combined. First - borns have been found to be more responsible and assertive than those born in other birth-order positions and tend to rise to positions of leadership more often than others; more first - borns have served in the U.S. Congress and as U.S. presidents than have those born in other birth - ­order positions. However, studies have shown that first-borns tend to be more subject to stress and were considered problem children more often than later-borns.         Second-born and/or middle children demonstrate markedly different tendencies from first­borns. They tend to feel inferior to the older child or children because it is difficult for them to comprehend that their lower level of achievement is a function of age rather than ability, and they often try to succeed in areas other than those in which their older sibling or siblings excel. They tend to be more trusting, accepting, and focused on others than the more self-centered first-borns, and they tend to have a comparatively higher level of success in team sports than do first-borns or only children, who more often excel in individual sports.         The last-born child is the one who tends to be the eternal baby of the family and thus often exhibits a strong sense of security. Last-borns collectively achieve the highest degree of social success and demonstrate the highest levels of self - esteem of all the birth-order positions. They often exhibit less competitiveness than older brothers and sisters and are more likely to take part in less competitive group games or in social organizations such as sororities and fraternities.         Only children tend to exhibit some of the main characteristics of first-borns and some of the characteristics of last-borns. Only children tend to exhibit the strong sense of security and self­esteem exhibited by last-borns while, like first-borns, they are more achievement oriented and more likely than middle-or last-borns to achieve academic success. However, only children tend to have the most problems establishing close relationships and exhibit a lower need for affiliation than other children. Which of the following would be most likely to have a successful career but few close friendships?
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.         A considerable body of research has demonstrated a correlation between birth order and aspects such as temperament and behavior, and some psychologists believe that birth order significantly affects the development of personality. Psychologist Alfred Adler was a pioneer in the study of the relationship between birth order and personality. A key point in his research and in the hypothesis that he developed based on it was that it was not the actual numerical birth position that affected personality; instead, it was the similar responses in large numbers of families to children in specific birth order positions that had an effect. For example, first - borns, who have their parents to themselves initially and do not have to deal with siblings in the first part of their lives, tend to have their first socialization experiences with adults and therefore tend to find the process of peer socialization more difficult. In contrast, later-born children have to deal with siblings from the first moment of their lives and therefore tend to have stronger socialization skills.         Numerous studies since Adler’s have been conducted on the effect of birth order and personality. These studies have tended to classify birth order types into four different categories: first-born, second-born and/or middle, last, and only child.         Studies have consistently shown that first-bom children tend to exhibit similar, positive and negative personality traits. First-borns have consistently been linked with academic achievement in various studies; in one study, the number of National Merit scholarship winners who are first­ - borns was found to be equal to the number of second - and third-borns combined. First - borns have been found to be more responsible and assertive than those born in other birth-order positions and tend to rise to positions of leadership more often than others; more first - borns have served in the U.S. Congress and as U.S. presidents than have those born in other birth - ­order positions. However, studies have shown that first-borns tend to be more subject to stress and were considered problem children more often than later-borns.         Second-born and/or middle children demonstrate markedly different tendencies from first­borns. They tend to feel inferior to the older child or children because it is difficult for them to comprehend that their lower level of achievement is a function of age rather than ability, and they often try to succeed in areas other than those in which their older sibling or siblings excel. They tend to be more trusting, accepting, and focused on others than the more self-centered first-borns, and they tend to have a comparatively higher level of success in team sports than do first-borns or only children, who more often excel in individual sports.         The last-born child is the one who tends to be the eternal baby of the family and thus often exhibits a strong sense of security. Last-borns collectively achieve the highest degree of social success and demonstrate the highest levels of self - esteem of all the birth-order positions. They often exhibit less competitiveness than older brothers and sisters and are more likely to take part in less competitive group games or in social organizations such as sororities and fraternities.         Only children tend to exhibit some of the main characteristics of first-borns and some of the characteristics of last-borns. Only children tend to exhibit the strong sense of security and self­esteem exhibited by last-borns while, like first-borns, they are more achievement oriented and more likely than middle-or last-borns to achieve academic success. However, only children tend to have the most problems establishing close relationships and exhibit a lower need for affiliation than other children. Which 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 35 to 42.         A considerable body of research has demonstrated a correlation between birth order and aspects such as temperament and behavior, and some psychologists believe that birth order significantly affects the development of personality. Psychologist Alfred Adler was a pioneer in the study of the relationship between birth order and personality. A key point in his research and in the hypothesis that he developed based on it was that it was not the actual numerical birth position that affected personality; instead, it was the similar responses in large numbers of families to children in specific birth order positions that had an effect. For example, first - borns, who have their parents to themselves initially and do not have to deal with siblings in the first part of their lives, tend to have their first socialization experiences with adults and therefore tend to find the process of peer socialization more difficult. In contrast, later-born children have to deal with siblings from the first moment of their lives and therefore tend to have stronger socialization skills.         Numerous studies since Adler’s have been conducted on the effect of birth order and personality. These studies have tended to classify birth order types into four different categories: first-born, second-born and/or middle, last, and only child.         Studies have consistently shown that first-bom children tend to exhibit similar, positive and negative personality traits. First-borns have consistently been linked with academic achievement in various studies; in one study, the number of National Merit scholarship winners who are first­ - borns was found to be equal to the number of second - and third-borns combined. First - borns have been found to be more responsible and assertive than those born in other birth-order positions and tend to rise to positions of leadership more often than others; more first - borns have served in the U.S. Congress and as U.S. presidents than have those born in other birth - ­order positions. However, studies have shown that first-borns tend to be more subject to stress and were considered problem children more often than later-borns.         Second-born and/or middle children demonstrate markedly different tendencies from first­borns. They tend to feel inferior to the older child or children because it is difficult for them to comprehend that their lower level of achievement is a function of age rather than ability, and they often try to succeed in areas other than those in which their older sibling or siblings excel. They tend to be more trusting, accepting, and focused on others than the more self-centered first-borns, and they tend to have a comparatively higher level of success in team sports than do first-borns or only children, who more often excel in individual sports.         The last-born child is the one who tends to be the eternal baby of the family and thus often exhibits a strong sense of security. Last-borns collectively achieve the highest degree of social success and demonstrate the highest levels of self - esteem of all the birth-order positions. They often exhibit less competitiveness than older brothers and sisters and are more likely to take part in less competitive group games or in social organizations such as sororities and fraternities.         Only children tend to exhibit some of the main characteristics of first-borns and some of the characteristics of last-borns. Only children tend to exhibit the strong sense of security and self­esteem exhibited by last-borns while, like first-borns, they are more achievement oriented and more likely than middle-or last-borns to achieve academic success. However, only children tend to have the most problems establishing close relationships and exhibit a lower need for affiliation than other children. The word accepting in paragraph 4 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 35 to 42.         A considerable body of research has demonstrated a correlation between birth order and aspects such as temperament and behavior, and some psychologists believe that birth order significantly affects the development of personality. Psychologist Alfred Adler was a pioneer in the study of the relationship between birth order and personality. A key point in his research and in the hypothesis that he developed based on it was that it was not the actual numerical birth position that affected personality; instead, it was the similar responses in large numbers of families to children in specific birth order positions that had an effect. For example, first - borns, who have their parents to themselves initially and do not have to deal with siblings in the first part of their lives, tend to have their first socialization experiences with adults and therefore tend to find the process of peer socialization more difficult. In contrast, later-born children have to deal with siblings from the first moment of their lives and therefore tend to have stronger socialization skills.         Numerous studies since Adler’s have been conducted on the effect of birth order and personality. These studies have tended to classify birth order types into four different categories: first-born, second-born and/or middle, last, and only child.         Studies have consistently shown that first-bom children tend to exhibit similar, positive and negative personality traits. First-borns have consistently been linked with academic achievement in various studies; in one study, the number of National Merit scholarship winners who are first­ - borns was found to be equal to the number of second - and third-borns combined. First - borns have been found to be more responsible and assertive than those born in other birth-order positions and tend to rise to positions of leadership more often than others; more first - borns have served in the U.S. Congress and as U.S. presidents than have those born in other birth - ­order positions. However, studies have shown that first-borns tend to be more subject to stress and were considered problem children more often than later-borns.         Second-born and/or middle children demonstrate markedly different tendencies from first­borns. They tend to feel inferior to the older child or children because it is difficult for them to comprehend that their lower level of achievement is a function of age rather than ability, and they often try to succeed in areas other than those in which their older sibling or siblings excel. They tend to be more trusting, accepting, and focused on others than the more self-centered first-borns, and they tend to have a comparatively higher level of success in team sports than do first-borns or only children, who more often excel in individual sports.         The last-born child is the one who tends to be the eternal baby of the family and thus often exhibits a strong sense of security. Last-borns collectively achieve the highest degree of social success and demonstrate the highest levels of self - esteem of all the birth-order positions. They often exhibit less competitiveness than older brothers and sisters and are more likely to take part in less competitive group games or in social organizations such as sororities and fraternities.         Only children tend to exhibit some of the main characteristics of first-borns and some of the characteristics of last-borns. Only children tend to exhibit the strong sense of security and self­esteem exhibited by last-borns while, like first-borns, they are more achievement oriented and more likely than middle-or last-borns to achieve academic success. However, only children tend to have the most problems establishing close relationships and exhibit a lower need for affiliation than other children. Which of the sentences below expresses the essential information in the bold sentence in paragraph 3? Incorrect choices change the meaning in important ways or leave out essential information.
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.         A considerable body of research has demonstrated a correlation between birth order and aspects such as temperament and behavior, and some psychologists believe that birth order significantly affects the development of personality. Psychologist Alfred Adler was a pioneer in the study of the relationship between birth order and personality. A key point in his research and in the hypothesis that he developed based on it was that it was not the actual numerical birth position that affected personality; instead, it was the similar responses in large numbers of families to children in specific birth order positions that had an effect. For example, first - borns, who have their parents to themselves initially and do not have to deal with siblings in the first part of their lives, tend to have their first socialization experiences with adults and therefore tend to find the process of peer socialization more difficult. In contrast, later-born children have to deal with siblings from the first moment of their lives and therefore tend to have stronger socialization skills.         Numerous studies since Adler’s have been conducted on the effect of birth order and personality. These studies have tended to classify birth order types into four different categories: first-born, second-born and/or middle, last, and only child.         Studies have consistently shown that first-bom children tend to exhibit similar, positive and negative personality traits. First-borns have consistently been linked with academic achievement in various studies; in one study, the number of National Merit scholarship winners who are first­ - borns was found to be equal to the number of second - and third-borns combined. First - borns have been found to be more responsible and assertive than those born in other birth-order positions and tend to rise to positions of leadership more often than others; more first - borns have served in the U.S. Congress and as U.S. presidents than have those born in other birth - ­order positions. However, studies have shown that first-borns tend to be more subject to stress and were considered problem children more often than later-borns.         Second-born and/or middle children demonstrate markedly different tendencies from first­borns. They tend to feel inferior to the older child or children because it is difficult for them to comprehend that their lower level of achievement is a function of age rather than ability, and they often try to succeed in areas other than those in which their older sibling or siblings excel. They tend to be more trusting, accepting, and focused on others than the more self-centered first-borns, and they tend to have a comparatively higher level of success in team sports than do first-borns or only children, who more often excel in individual sports.         The last-born child is the one who tends to be the eternal baby of the family and thus often exhibits a strong sense of security. Last-borns collectively achieve the highest degree of social success and demonstrate the highest levels of self - esteem of all the birth-order positions. They often exhibit less competitiveness than older brothers and sisters and are more likely to take part in less competitive group games or in social organizations such as sororities and fraternities.         Only children tend to exhibit some of the main characteristics of first-borns and some of the characteristics of last-borns. Only children tend to exhibit the strong sense of security and self­esteem exhibited by last-borns while, like first-borns, they are more achievement oriented and more likely than middle-or last-borns to achieve academic success. However, only children tend to have the most problems establishing close relationships and exhibit a lower need for affiliation than other children. The word traits 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 35 to 42.         A considerable body of research has demonstrated a correlation between birth order and aspects such as temperament and behavior, and some psychologists believe that birth order significantly affects the development of personality. Psychologist Alfred Adler was a pioneer in the study of the relationship between birth order and personality. A key point in his research and in the hypothesis that he developed based on it was that it was not the actual numerical birth position that affected personality; instead, it was the similar responses in large numbers of families to children in specific birth order positions that had an effect. For example, first - borns, who have their parents to themselves initially and do not have to deal with siblings in the first part of their lives, tend to have their first socialization experiences with adults and therefore tend to find the process of peer socialization more difficult. In contrast, later-born children have to deal with siblings from the first moment of their lives and therefore tend to have stronger socialization skills.         Numerous studies since Adler’s have been conducted on the effect of birth order and personality. These studies have tended to classify birth order types into four different categories: first-born, second-born and/or middle, last, and only child.         Studies have consistently shown that first-bom children tend to exhibit similar, positive and negative personality traits. First-borns have consistently been linked with academic achievement in various studies; in one study, the number of National Merit scholarship winners who are first­ - borns was found to be equal to the number of second - and third-borns combined. First - borns have been found to be more responsible and assertive than those born in other birth-order positions and tend to rise to positions of leadership more often than others; more first - borns have served in the U.S. Congress and as U.S. presidents than have those born in other birth - ­order positions. However, studies have shown that first-borns tend to be more subject to stress and were considered problem children more often than later-borns.         Second-born and/or middle children demonstrate markedly different tendencies from first­borns. They tend to feel inferior to the older child or children because it is difficult for them to comprehend that their lower level of achievement is a function of age rather than ability, and they often try to succeed in areas other than those in which their older sibling or siblings excel. They tend to be more trusting, accepting, and focused on others than the more self-centered first-borns, and they tend to have a comparatively higher level of success in team sports than do first-borns or only children, who more often excel in individual sports.         The last-born child is the one who tends to be the eternal baby of the family and thus often exhibits a strong sense of security. Last-borns collectively achieve the highest degree of social success and demonstrate the highest levels of self - esteem of all the birth-order positions. They often exhibit less competitiveness than older brothers and sisters and are more likely to take part in less competitive group games or in social organizations such as sororities and fraternities.         Only children tend to exhibit some of the main characteristics of first-borns and some of the characteristics of last-borns. Only children tend to exhibit the strong sense of security and self­esteem exhibited by last-borns while, like first-borns, they are more achievement oriented and more likely than middle-or last-borns to achieve academic success. However, only children tend to have the most problems establishing close relationships and exhibit a lower need for affiliation than other children. The word body in paragraph 1 could best be replaced by _________.
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 estimated that over 99 percent of all species that ever existed have become extinct. What causes extinction? When a species is no longer adapted to a changed environment, it may perish. The exact causes of a species' death vary from situation to situation. Rapid ecological change may render an environment hostile to a species. For example, temperatures may change and a species may not be able to adapt. Food Resources may be affected by environmental changes, which will then cause problems for a species requiring these resources. Other species may become better adapted to an environment, resulting in competition and, ultimately, in the death of a species.         The fossil record reveals that extinction has occurred throughout the history of Earth. Recent analyses have also revealed that on some occasions many species became extinct at the same time - a mass extinction. One of the best-known examples of mass extinction occurred 65 million years ago with the demise of dinosaurs and many other forms of life. Perhaps the largest mass extinction was the one that occurred 225 million years ago. When approximately 95 percent of all species died, mass extinctions can be caused by a relatively rapid change in the environment and can be worsened by the close interrelationship of many species. If, for example, something were to happen to destroy much of the plankton in the oceans, then the oxygen content of Earth would drop, affection even organisms not living in the oceans. Such a change would probably lead to a mass extinction.         One interesting, and controversial, finding is that extinctions during the past 250 million years have tended to be more intense every 26 million years. This periodic extinction might be due to intersection of the Earth’s orbit with a cloud of comets, but this theory is purely speculative. Some researchers have also speculated that extinction may often be random. That is, certain species may be eliminated and others may survive for no particular reason. A species’ survival may have nothing to do with its ability or inability to adapt. If so, some of evolutionary history may reflect a sequence of essentially random events. In paragraph 3, the author makes which of the following statements about a species’ survival?
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 estimated that over 99 percent of all species that ever existed have become extinct. What causes extinction? When a species is no longer adapted to a changed environment, it may perish. The exact causes of a species' death vary from situation to situation. Rapid ecological change may render an environment hostile to a species. For example, temperatures may change and a species may not be able to adapt. Food Resources may be affected by environmental changes, which will then cause problems for a species requiring these resources. Other species may become better adapted to an environment, resulting in competition and, ultimately, in the death of a species.         The fossil record reveals that extinction has occurred throughout the history of Earth. Recent analyses have also revealed that on some occasions many species became extinct at the same time - a mass extinction. One of the best-known examples of mass extinction occurred 65 million years ago with the demise of dinosaurs and many other forms of life. Perhaps the largest mass extinction was the one that occurred 225 million years ago. When approximately 95 percent of all species died, mass extinctions can be caused by a relatively rapid change in the environment and can be worsened by the close interrelationship of many species. If, for example, something were to happen to destroy much of the plankton in the oceans, then the oxygen content of Earth would drop, affection even organisms not living in the oceans. Such a change would probably lead to a mass extinction.         One interesting, and controversial, finding is that extinctions during the past 250 million years have tended to be more intense every 26 million years. This periodic extinction might be due to intersection of the Earth’s orbit with a cloud of comets, but this theory is purely speculative. Some researchers have also speculated that extinction may often be random. That is, certain species may be eliminated and others may survive for no particular reason. A species’ survival may have nothing to do with its ability or inability to adapt. If so, some of evolutionary history may reflect a sequence of essentially random events. What does the author say in paragraph 1 regarding most species in Earth’s history?