questions 1-9 are based on the following passage:

This passage is adapted from John R. Skoyles and Dorion Sagan, Up from Dragons. ©2002 The McGraw-Hill Companies. Here, the authors discuss the evolution of human intelligence.

We are a bright species. We have gone into space and walked on the moon. Yet you would never have guessed that if you traveled back to between 100,000 and 40,000 years ago. At that time our Homo sapiens ancestors and Neanderthals (Homo neanderthalensis) coexisted. Neanderthals were like us but physically stronger, with large bones and teeth, protruding brows and face, and hardly a chin. Perhaps what we lacked in brawn we made up for in brains. But for most of our history, our species was not bright enough to act very differently from the Neanderthals, let alone be more successful than they were. Only around 40,000 to 32,000 years ago, in Western Asia and Europe, did Neanderthal people disappear, to be replaced by our species.

(1) Why did we coexist with Neanderthals for 60,000 years—a far longer case of hominids living side by side than any other in human history? (2) And why did we eventually win out? (3) Brains alone cannot provide the answer, as Neanderthals may in fact have had the larger ones. Perhaps they lacked the long vocal chamber needed for speech. (4) Equal certainty exists among those who study the base of their skulls that they did and that they did not. If they did lack one, then this could be the explanation, but maybe not, since even without a voice box, gestures can communicate, as can be seen among the deaf. (5) Indeed, hunters find advantages in using sign language (speech sounds would warn off potential prey), and not just while hunting but in everyday life. (6) Anthropologists find that hunter-gatherers use sophisticated sign languages to complement their speech. (7) Sign language might even have other advantages—evidence even suggests that it is easier to learn than speech: deaf children start to pick up signs earlier than hearing ones learn to speak. (8) So “spoken speech” is not in all ways superior to “signed speech.” (9) It is not something that can explain our replacement of the Neanderthals.

The reason we—anatomically modern humans—won out lies, we suspect, not in being brighter or better able to speak but in our very physical frailty and our resulting need to exploit our minds. Neanderthals, stronger than us, did not need to take this route. They could survive with their physical strength rather than tapping the potential of their brains. An analogy is with countries: the richest ones, such as Switzerland, Finland, Singapore, and Japan, are not blessed with, but rather lack, natural resources. Without them, they have been forced to use their brains to innovate, providing products and services ranging from cell phones to diplomacy.

1.The authors use the phrase “equal certainty” (paragraph 2) to make the point that

2. The authors of this passage would most likely agree with which of the following statements?

3. Which choice provides the best evidence for the answer to the previous question?

4. The term Cro-Magnon refers to the earliest members of the species H. sapiens. Which of following statements is most justified by the diagram in Figure 1?

5. If the fossil record indicated in the accompanying diagram is assumed to be accurate and complete, what is the longest period of time that any single hominid species lived on the earth?

6.

questions 1-9 are based on the following passage:

This passage is adapted from John R. Skoyles and Dorion Sagan, Up from Dragons. ©2002 The McGraw-Hill Companies. Here, the authors discuss the evolution of human intelligence.

We are a bright species. We have gone into space and walked on the moon. Yet you would never have guessed that if you traveled back to between 100,000 and 40,000 years ago. At that time our Homo sapiens ancestors and Neanderthals (Homo neanderthalensis) coexisted. Neanderthals were like us but physically stronger, with large bones and teeth, protruding brows and face, and hardly a chin. Perhaps what we lacked in brawn we made up for in brains. But for most of our history, our species was not bright enough to act very differently from the Neanderthals, let alone be more successful than they were. Only around 40,000 to 32,000 years ago, in Western Asia and Europe, did Neanderthal people disappear, to be replaced by our species.

(1) Why did we coexist with Neanderthals for 60,000 years—a far longer case of hominids living side by side than any other in human history? (2) And why did we eventually win out? (3) Brains alone cannot provide the answer, as Neanderthals may in fact have had the larger ones. Perhaps they lacked the long vocal chamber needed for speech. (4) Equal certainty exists among those who study the base of their skulls that they did and that they did not. If they did lack one, then this could be the explanation, but maybe not, since even without a voice box, gestures can communicate, as can be seen among the deaf. (5) Indeed, hunters find advantages in using sign language (speech sounds would warn off potential prey), and not just while hunting but in everyday life. (6) Anthropologists find that hunter-gatherers use sophisticated sign languages to complement their speech. (7) Sign language might even have other advantages—evidence even suggests that it is easier to learn than speech: deaf children start to pick up signs earlier than hearing ones learn to speak. (8) So “spoken speech” is not in all ways superior to “signed speech.” (9) It is not something that can explain our replacement of the Neanderthals.

The reason we—anatomically modern humans—won out lies, we suspect, not in being brighter or better able to speak but in our very physical frailty and our resulting need to exploit our minds. Neanderthals, stronger than us, did not need to take this route. They could survive with their physical strength rather than tapping the potential of their brains. An analogy is with countries: the richest ones, such as Switzerland, Finland, Singapore, and Japan, are not blessed with, but rather lack, natural resources. Without them, they have been forced to use their brains to innovate, providing products and services ranging from cell phones to diplomacy.

6.Which of the following best describes how the diagram supports the main argument of this passage?

7. The authors mention that “hunter-gatherers use sophisticated sign language” (paragraph 2 sentence 6) primarily in order to

8. In paragraph 3, “tapping” most nearly means

9. The authors mention “cell phones” and “diplomacy” (paragraph 3 last sentence) primarily as examples of

questions 10-18 are based on the following passage:

This passage is adapted from Reginald V. Kaplan, “Elements of Explanation.” ©2016 College Hill Coaching.

The march of human intellectual progress over the last 2,500 years has been, in brief, a journey from teleological to mechanistic explanations. We have moved, slowly and tortuously, from beliefs about the “purpose” of phenomena like lightning and earthquakes to debates about which theories, equations, and mechanisms best represent them. We’ve deepened our understandings by strengthening our mode of explanation. But we can’t pat ourselves on the back just yet. We are all—even the most scientific among us—still plagued by faulty intuitions.

(1) We are all born teleologists. From the Latin “telos” or “goal,” teleology is the act of explaining phenomena in terms of their presumed purposes or desires, rather than their causes: we have brains so we can think, the sun shines so we can be warm, rain falls so we can have fresh water. (2) Such explanations come so easily to us that we find it hard to appreciate how misguided and unhelpful they are. (3) They fail because they can’t predict the future as accurately as mechanistic explanations can: the laws of chemistry predict reactions, the laws of fluid dynamics predict tomorrow’s weather, and the laws of physics predict when and where our interplanetary probes will land.

Teleological explanations seem intuitive because our consciousness is a constant stream of urge followed by action: we are thirsty so we get some water, we are frightened so we run away, we want to make a friend so we say hello. These urge-action connections are so constant inside of our brains that we fool ourselves into thinking that they apply outside of our brains as well. We program ourselves to mistake urges for causes.

Teleological explanations fail when we try to describe phenomena that are outside of our skulls: rocks do not fall because they want to return to the earth, tornadoes don’t form because the sky gods are angry. We know now that rocks and clouds lack the mental machinery required for desire or anger. The real explanations for these phenomena are found in the mechanisms of physics and meteorology.

Still, when a friend asks you why you’re not going to a party, you’re not going to describe the mechanisms by which your brain processed the information, weighing rational and emotional inputs in various cortical and limbic centers, and produced a decision-response. You’re just going to say you don’t want to go. In personal conversations, teleological explanations are fine, if crude.

Even the most clear-minded scientist slides into teleology from time to time when describing natural phenomena to laypeople. When, in a recent documentary, evolutionary biologist Neil Shubin stated that “to combat the dry air on land, reptiles evolved a new kind of skin” he wasn’t disavowing the theory of natural selection and embracing the belief that an animal can evolve a feature just to satisfy a need. He was merely trying to explain something complex in terms we could understand.

The superior accuracy of mechanistic explanations comes at a price. They are not only more complex, but also more unsettling. If I skipped the party because of electro-chemical reactions governed by the laws of physics and chemistry, where is my free will?

We will only continue our progress toward deeper understanding if we see our self-centered intuitions as obstacles rather than guides to our pursuit. If we are to cure diseases, eradicate social scourges, and create a better world, we must embrace the disciplined, if counterintuitive, methods of scientific mechanism.

10. The first paragraph characterizes the “march of human intellectual progress” as

Questions 10-18 are based on the following passage:

This passage is adapted from Reginald V. Kaplan, “Elements of Explanation.” ©2016 College Hill Coaching.

The march of human intellectual progress over the last 2,500 years has been, in brief, a journey from teleological to mechanistic explanations. We have moved, slowly and tortuously, from beliefs about the “purpose” of phenomena like lightning and earthquakes to debates about which theories, equations, and mechanisms best represent them. We’ve deepened our understandings by strengthening our mode of explanation. But we can’t pat ourselves on the back just yet. We are all—even the most scientific among us—still plagued by faulty intuitions.

(1) We are all born teleologists. From the Latin “telos” or “goal,” teleology is the act of explaining phenomena in terms of their presumed purposes or desires, rather than their causes: we have brains so we can think, the sun shines so we can be warm, rain falls so we can have fresh water. (2) Such explanations come so easily to us that we find it hard to appreciate how misguided and unhelpful they are. (3) They fail because they can’t predict the future as accurately as mechanistic explanations can: the laws of chemistry predict reactions, the laws of fluid dynamics predict tomorrow’s weather, and the laws of physics predict when and where our interplanetary probes will land.

Teleological explanations seem intuitive because our consciousness is a constant stream of urge followed by action: we are thirsty so we get some water, we are frightened so we run away, we want to make a friend so we say hello. These urge-action connections are so constant inside of our brains that we fool ourselves into thinking that they apply outside of our brains as well. We program ourselves to mistake urges for causes.

Teleological explanations fail when we try to describe phenomena that are outside of our skulls: rocks do not fall because they want to return to the earth, tornadoes don’t form because the sky gods are angry. We know now that rocks and clouds lack the mental machinery required for desire or anger. The real explanations for these phenomena are found in the mechanisms of physics and meteorology.

Still, when a friend asks you why you’re not going to a party, you’re not going to describe the mechanisms by which your brain processed the information, weighing rational and emotional inputs in various cortical and limbic centers, and produced a decision-response. You’re just going to say you don’t want to go. In personal conversations, teleological explanations are fine, if crude.

Even the most clear-minded scientist slides into teleology from time to time when describing natural phenomena to laypeople. When, in a recent documentary, evolutionary biologist Neil Shubin stated that “to combat the dry air on land, reptiles evolved a new kind of skin” he wasn’t disavowing the theory of natural selection and embracing the belief that an animal can evolve a feature just to satisfy a need. He was merely trying to explain something complex in terms we could understand.

The superior accuracy of mechanistic explanations comes at a price. They are not only more complex, but also more unsettling. If I skipped the party because of electro-chemical reactions governed by the laws of physics and chemistry, where is my free will?

We will only continue our progress toward deeper understanding if we see our self-centered intuitions as obstacles rather than guides to our pursuit. If we are to cure diseases, eradicate social scourges, and create a better world, we must embrace the disciplined, if counterintuitive, methods of scientific mechanism.

11. The first paragraph is notable primarily for its use of

12. In line 4, “mechanistic” most nearly means

13. To the author, the examples in lines 10-11 in paragraph 2 (“we have brains . . . fresh water”) primarily represent

14. The author faults teleological explanations primarily for their

15. Which choice provides the best evidence for the answer to the previous question?

Questions 10-18 are based on the following passage:

This passage is adapted from Reginald V. Kaplan, “Elements of Explanation.” ©2016 College Hill Coaching.

The march of human intellectual progress over the last 2,500 years has been, in brief, a journey from teleological to mechanistic explanations. We have moved, slowly and tortuously, from beliefs about the “purpose” of phenomena like lightning and earthquakes to debates about which theories, equations, and mechanisms best represent them. We’ve deepened our understandings by strengthening our mode of explanation. But we can’t pat ourselves on the back just yet. We are all—even the most scientific among us—still plagued by faulty intuitions.

(1) We are all born teleologists. From the Latin “telos” or “goal,” teleology is the act of explaining phenomena in terms of their presumed purposes or desires, rather than their causes: we have brains so we can think, the sun shines so we can be warm, rain falls so we can have fresh water. (2) Such explanations come so easily to us that we find it hard to appreciate how misguided and unhelpful they are. (3) They fail because they can’t predict the future as accurately as mechanistic explanations can: the laws of chemistry predict reactions, the laws of fluid dynamics predict tomorrow’s weather, and the laws of physics predict when and where our interplanetary probes will land.

Teleological explanations seem intuitive because our consciousness is a constant stream of urge followed by action: we are thirsty so we get some water, we are frightened so we run away, we want to make a friend so we say hello. These urge-action connections are so constant inside of our brains that we fool ourselves into thinking that they apply outside of our brains as well. We program ourselves to mistake urges for causes.

Teleological explanations fail when we try to describe phenomena that are outside of our skulls: rocks do not fall because they want to return to the earth, tornadoes don’t form because the sky gods are angry. We know now that rocks and clouds lack the mental machinery required for desire or anger. The real explanations for these phenomena are found in the mechanisms of physics and meteorology.

Still, when a friend asks you why you’re not going to a party, you’re not going to describe the mechanisms by which your brain processed the information, weighing rational and emotional inputs in various cortical and limbic centers, and produced a decision-response. You’re just going to say you don’t want to go. In personal conversations, teleological explanations are fine, if crude.

Even the most clear-minded scientist slides into teleology from time to time when describing natural phenomena to laypeople. When, in a recent documentary, evolutionary biologist Neil Shubin stated that “to combat the dry air on land, reptiles evolved a new kind of skin” he wasn’t disavowing the theory of natural selection and embracing the belief that an animal can evolve a feature just to satisfy a need. He was merely trying to explain something complex in terms we could understand.

The superior accuracy of mechanistic explanations comes at a price. They are not only more complex, but also more unsettling. If I skipped the party because of electro-chemical reactions governed by the laws of physics and chemistry, where is my free will?

We will only continue our progress toward deeper understanding if we see our self-centered intuitions as obstacles rather than guides to our pursuit. If we are to cure diseases, eradicate social scourges, and create a better world, we must embrace the disciplined, if counterintuitive, methods of scientific mechanism.

16. According to the author, Neil Shubin’s error was that he

17. The main function of the seventh paragraph is to

18. The tone of the final is best described as

Questions 19-26 are based on the following passage:

This passage is from Wassily Kandinsky, Concerning the Spiritual in Art. ©1997 Dover Publications. Reprinted by permission of Dover Publications. In this essay, Kandinsky (1866–1944), a Russian abstract painter, discusses the relationship between Primitivism, a movement to revive the art of ancient peoples, and Materialism, a movement that denies the existence or value of the spiritual realm.

Every work of art is the child of its age and, in many cases, the mother of our emotions. It follows that each period of culture produces an art of its own which can never be repeated. Efforts to revive the art-principles of the past will at best produce an art that is stillborn. It is impossible for us to live and feel as did the ancient Greeks. In the same way those who strive to follow the Greek methods in sculpture achieve only a similarity of form, the work remaining soulless for all time. Such imitation is mere aping. Externally the monkey completely resembles the human being; he will sit holding a book in front of his nose, and turn over the pages with a thoughtful aspect, but his actions have for him no real meaning.

(1) There is, however, in art another kind of external similarity that is founded on a fundamental truth. (2) When there is a similarity of inner tendency in the whole moral and spiritual atmosphere, a similarity of ideals, at first closely pursued but later lost to sight, a similarity in the inner feeling of any one period to that of another, the logical result will be a revival of the external forms which served to express those inner feelings in an earlier age. (3) An example of this today is our sympathy, our spiritual relationship, with the Primitives. Like ourselves, these artists sought to express in their work only internal truths, renouncing in consequence all considerations of external form.

(1) This all-important spark of inner life today is at present only a spark. (2) Our minds, which are even now only just awakening after years of materialism, are infected with the despair of unbelief, of lack of purpose and ideal. (3) The nightmare of materialism, which has turned the life of the universe into an evil, useless game, is not yet past. (4) It holds the awakening soul still in its grip. (5) Only a feeble light glimmers like a tiny star in a vast gulf of darkness. (6) This feeble light is but a presentiment, and the soul, when it sees it, trembles in doubt whether the light is not a dream, and the gulf of darkness reality. (7) This doubt and the still-harsh tyranny of the materialistic philosophy divide our soul sharply from that of the Primitives. (8) Our soul rings cracked when we seem to play upon it, as does a costly vase, long buried in the earth, which is found to have a flaw when it is dug up once more. (9) For this reason, the Primitive phase, through which we are now passing, with its temporary similarity of form, can only be of short duration.

19. The passage is primarily concerned with

20. In the first sentence, the contrast between “child” and the “mother” is primarily one of

Questions 19-26 are based on the following passage:

This passage is from Wassily Kandinsky, Concerning the Spiritual in Art. ©1997 Dover Publications. Reprinted by permission of Dover Publications. In this essay, Kandinsky (1866–1944), a Russian abstract painter, discusses the relationship between Primitivism, a movement to revive the art of ancient peoples, and Materialism, a movement that denies the existence or value of the spiritual realm.

Every work of art is the child of its age and, in many cases, the mother of our emotions. It follows that each period of culture produces an art of its own which can never be repeated. Efforts to revive the art-principles of the past will at best produce an art that is stillborn. It is impossible for us to live and feel as did the ancient Greeks. In the same way those who strive to follow the Greek methods in sculpture achieve only a similarity of form, the work remaining soulless for all time. Such imitation is mere aping. Externally the monkey completely resembles the human being; he will sit holding a book in front of his nose, and turn over the pages with a thoughtful aspect, but his actions have for him no real meaning.

(1) There is, however, in art another kind of external similarity that is founded on a fundamental truth. (2) When there is a similarity of inner tendency in the whole moral and spiritual atmosphere, a similarity of ideals, at first closely pursued but later lost to sight, a similarity in the inner feeling of any one period to that of another, the logical result will be a revival of the external forms which served to express those inner feelings in an earlier age. (3) An example of this today is our sympathy, our spiritual relationship, with the Primitives. Like ourselves, these artists sought to express in their work only internal truths, renouncing in consequence all considerations of external form.

(1) This all-important spark of inner life today is at present only a spark. (2) Our minds, which are even now only just awakening after years of materialism, are infected with the despair of unbelief, of lack of purpose and ideal. (3) The nightmare of materialism, which has turned the life of the universe into an evil, useless game, is not yet past. (4) It holds the awakening soul still in its grip. (5) Only a feeble light glimmers like a tiny star in a vast gulf of darkness. (6) This feeble light is but a presentiment, and the soul, when it sees it, trembles in doubt whether the light is not a dream, and the gulf of darkness reality. (7) This doubt and the still-harsh tyranny of the materialistic philosophy divide our soul sharply from that of the Primitives. (8) Our soul rings cracked when we seem to play upon it, as does a costly vase, long buried in the earth, which is found to have a flaw when it is dug up once more. (9) For this reason, the Primitive phase, through which we are now passing, with its temporary similarity of form, can only be of short duration.

21. In paragraph 1, “aspect” most nearly means

22. Which of the following best exemplifies the “truth” mentioned in paragraph 2?

23. According to the passage, materialism affects artists primarily by

24. Which choice provides the best evidence for the answer to the previous question?

25. The author uses the phrase “trembles in doubt” (paragraph 3) in order to emphasize his belief that

Questions 19-26 are based on the following passage:

This passage is from Wassily Kandinsky, Concerning the Spiritual in Art. ©1997 Dover Publications. Reprinted by permission of Dover Publications. In this essay, Kandinsky (1866–1944), a Russian abstract painter, discusses the relationship between Primitivism, a movement to revive the art of ancient peoples, and Materialism, a movement that denies the existence or value of the spiritual realm.

Every work of art is the child of its age and, in many cases, the mother of our emotions. It follows that each period of culture produces an art of its own which can never be repeated. Efforts to revive the art-principles of the past will at best produce an art that is stillborn. It is impossible for us to live and feel as did the ancient Greeks. In the same way those who strive to follow the Greek methods in sculpture achieve only a similarity of form, the work remaining soulless for all time. Such imitation is mere aping. Externally the monkey completely resembles the human being; he will sit holding a book in front of his nose, and turn over the pages with a thoughtful aspect, but his actions have for him no real meaning.

(1) There is, however, in art another kind of external similarity that is founded on a fundamental truth. (2) When there is a similarity of inner tendency in the whole moral and spiritual atmosphere, a similarity of ideals, at first closely pursued but later lost to sight, a similarity in the inner feeling of any one period to that of another, the logical result will be a revival of the external forms which served to express those inner feelings in an earlier age. (3) An example of this today is our sympathy, our spiritual relationship, with the Primitives. Like ourselves, these artists sought to express in their work only internal truths, renouncing in consequence all considerations of external form.

(1) This all-important spark of inner life today is at present only a spark. (2) Our minds, which are even now only just awakening after years of materialism, are infected with the despair of unbelief, of lack of purpose and ideal. (3) The nightmare of materialism, which has turned the life of the universe into an evil, useless game, is not yet past. (4) It holds the awakening soul still in its grip. (5) Only a feeble light glimmers like a tiny star in a vast gulf of darkness. (6) This feeble light is but a presentiment, and the soul, when it sees it, trembles in doubt whether the light is not a dream, and the gulf of darkness reality. (7) This doubt and the still-harsh tyranny of the materialistic philosophy divide our soul sharply from that of the Primitives. (8) Our soul rings cracked when we seem to play upon it, as does a costly vase, long buried in the earth, which is found to have a flaw when it is dug up once more. (9) For this reason, the Primitive phase, through which we are now passing, with its temporary similarity of form, can only be of short duration.

26. In paragraph 3, the “costly vase” represents

Questions 27-35 are based on the following passage:

The following passage discusses the possibility that there is life on Mars. Interest in the subject reached a peak when NASA sent two unmanned spacecraft to Mars in 1975. After 10 months, Vikings 1 and 2 entered orbits around The Red Planet and released landers.

When the first of the two Viking landers touched down on Martian soil on July 20, 1976, and began to send camera images back to Earth, the scientists at the Jet Propulsion Laboratory (J.P.L.) could not suppress a certain nervous anticipation, like people who hold a ticket to a lottery they have a one-in-a-million chance of winning. The first photographs that arrived, however, did not contain any evidence of life. [4] What revealed itself to them was merely a barren landscape littered with rocks and boulders. [2] The view resembled nothing so much as a flat section of desert—in fact, the winning entry in a contest at J.P.L. for the photograph most accurately predicting what Mars would look like was a snapshot taken in a particularly arid section of the Mojave Desert.

The scientists were soon ready to turn their attention from visible life to microorganisms. [2] The twin Viking landers carried three experiments designed to detect current biological activity and one to detect organic compounds, because re-searchers thought it possible that life had developed on early Mars just as it is thought to have developed on Earth, through the gradual chemical evolution of complex organic molecules. To detect biological activity, Martian soil samples were treated with various nutrients that would produce characteristic by-products if life-forms were active in the soil. The results from all three experiments were inconclusive. The fourth experiment heated a soil sample to look for signs of organic material but found none, an unexpected result because at least organic compounds from the steady bombardment of the Martian surface by meteorites were thought to have been present

The absence of organic materials, some scientists speculated, was the result of intense ultraviolet radiation penetrating the atmosphere of Mars and destroying organic compounds in the soil. [4] Although Mars’s atmosphere still has a high percentage of carbon dioxide, the density of the carbon dioxide used to be greater, thus protecting the surface from harmful rays of the sun. [2] Gradually, this concentration thinned as more carbon dioxide was converted into rock. [4] This means that even if life had gotten a start on early Mars, it could not have survived the exposure to ultraviolet radiation when the atmosphere thinned. Mars never developed a protective layer of ozone as Earth did.    

Despite the disappointing Viking results, there are those who still keep open the possibility of life on Mars. They point out that the Viking data cannot be considered the final word on Martian life because the two landers only sampled two limited—and uninteresting—sites. [2] The Viking landing sites were not chosen for what they might tell of the planet’s biology. They were chosen primarily because they appeared to be safe for landing a spacecraft. The landing sites were on parts of the Martian plains that appeared relatively featureless from orbital photographs. The type of Martian terrain that these researchers suggest may be a possible hiding place for active life has an earthly parallel: the ice-free region of southern Victoria Land, Antarctica, where the temperatures in some dry valleys aver-age below zero. [4] Organisms known as endoliths, a form of blue-green algae that has adapted to this harsh environment, were found living inside certain translucent, porous rocks in these Antarctic valleys. The argument based on this discovery is that if life did exist on early Mars, it is possible that it escaped worsening conditions by similarly seeking refuge in rocks. Skeptics object, however, stating that Mars in its present state is simply too dry, even compared with Antarctic valleys, to sustain any life whatsoever.

Should Mars eventually prove to be completely barren of life, as some suspect, then this would have a significant impact on the current view of the chemical origin of life. It could be much more difficult to get life started on a planet than scientists thought before the Viking landings.

27. The researchers’ argument that life may exist in Martian rocks rests on the idea that

28. Which choice provides the best evidence for the answer to the previous question?

29. The passage suggests that an important difference between Mars and Earth is that, unlike Earth, Mars

30. Which choice provides the best evidence for the answer to the previous question?

Questions 27-35 are based on the following passage:

The following passage discusses the possibility that there is life on Mars. Interest in the subject reached a peak when NASA sent two unmanned spacecraft to Mars in 1975. After 10 months, Vikings 1 and 2 entered orbits around The Red Planet and released landers.

When the first of the two Viking landers touched down on Martian soil on July 20, 1976, and began to send camera images back to Earth, the scientists at the Jet Propulsion Laboratory (J.P.L.) could not suppress a certain nervous anticipation, like people who hold a ticket to a lottery they have a one-in-a-million chance of winning. The first photographs that arrived, however, did not contain any evidence of life. [4] What revealed itself to them was merely a barren landscape littered with rocks and boulders. [2] The view resembled nothing so much as a flat section of desert—in fact, the winning entry in a contest at J.P.L. for the photograph most accurately predicting what Mars would look like was a snapshot taken in a particularly arid section of the Mojave Desert.

The scientists were soon ready to turn their attention from visible life to microorganisms. [2] The twin Viking landers carried three experiments designed to detect current biological activity and one to detect organic compounds, because re-searchers thought it possible that life had developed on early Mars just as it is thought to have developed on Earth, through the gradual chemical evolution of complex organic molecules. To detect biological activity, Martian soil samples were treated with various nutrients that would produce characteristic by-products if life-forms were active in the soil. The results from all three experiments were inconclusive. The fourth experiment heated a soil sample to look for signs of organic material but found none, an unexpected result because at least organic compounds from the steady bombardment of the Martian surface by meteorites were thought to have been present

The absence of organic materials, some scientists speculated, was the result of intense ultraviolet radiation penetrating the atmosphere of Mars and destroying organic compounds in the soil. [4] Although Mars’s atmosphere still has a high percentage of carbon dioxide, the density of the carbon dioxide used to be greater, thus protecting the surface from harmful rays of the sun. [2] Gradually, this concentration thinned as more carbon dioxide was converted into rock. [4] This means that even if life had gotten a start on early Mars, it could not have survived the exposure to ultraviolet radiation when the atmosphere thinned. Mars never developed a protective layer of ozone as Earth did.    

Despite the disappointing Viking results, there are those who still keep open the possibility of life on Mars. They point out that the Viking data cannot be considered the final word on Martian life because the two landers only sampled two limited—and uninteresting—sites. [2] The Viking landing sites were not chosen for what they might tell of the planet’s biology. They were chosen primarily because they appeared to be safe for landing a spacecraft. The landing sites were on parts of the Martian plains that appeared relatively featureless from orbital photographs. The type of Martian terrain that these researchers suggest may be a possible hiding place for active life has an earthly parallel: the ice-free region of southern Victoria Land, Antarctica, where the temperatures in some dry valleys aver-age below zero. [4] Organisms known as endoliths, a form of blue-green algae that has adapted to this harsh environment, were found living inside certain translucent, porous rocks in these Antarctic valleys. The argument based on this discovery is that if life did exist on early Mars, it is possible that it escaped worsening conditions by similarly seeking refuge in rocks. Skeptics object, however, stating that Mars in its present state is simply too dry, even compared with Antarctic valleys, to sustain any life whatsoever.

Should Mars eventually prove to be completely barren of life, as some suspect, then this would have a significant impact on the current view of the chemical origin of life. It could be much more difficult to get life started on a planet than scientists thought before the Viking landings.

31. In describing the scientists’ reaction to the Viking images of Mars, the author’s reference to the lottery (paragraph 1) implies that

32. According to the passage, the surface of Mars most resembles

33. The main purpose of the fourth paragraph is to indicate that

34. Which of the following facts from the passage is supported by the information in the graph?

35. Ozone is a gas composed entirely of oxygen molecules. What information in the graph supports the statement in the passage that Mars never developed a protective layer of ozone as Earth did?