2017年GRE阅读理解冲刺题及答案（三）

>>GRE考试试题及答案：2017年GRE阅读理解冲刺题及答案（三）

P1

Biologists have long maintained that two groups of pinnipeds, sea lions and walruses, are descended from a terrestrial bearlike animal, whereas the remaining group, seals, shares an ancestor with weasels.

But the recent discovery of detailed similarities in the skeletal structure of the flippers in all three groups undermines the attempt to explain away superficial resemblance as due to convergent evolution—the independent development of similarities between unrelated groups in response to similar environmental pressures.

Flippers may indeed be a necessary response to aquatic life; turtles, whales, and dugongs also have them.

But the common detailed design found among the pinnipeds probably indicates a common ancestor.

Moreover, walruses and seals drive themselves through the water with thrusts of their hind flippers, but sea lions use their front flippers.

If anatomical similarity in the flippers resulted from similar environmental pressures, as posited by the convergent-evolution theory, one would expect walruses and seals, but not seals and sea lions, to have similar flippers. (162 words)

1. The author implies that which of the following was part of the long-standing view concerning pinnipeds?

□A Pinnipeds are all descended from a terrestrial bearlike animal.

□B Pinnipeds share a common ancestor with turtles, whales, and dugongs

□C Similarities among pinnipeds are due to their all having had to adapt to aquatic life.

2. The author implies which of the following about the fact that turtles, whales, and dugongs all have flippers?

○A It can be explained by the hypothesis that turtles, whales, and dugongs are very closely related.

○B It can be explained by the idea of convergent evolution.

○C It suggests that turtles, whales, and dugongs evolved in separate parts of the world

○D It undermines the view that turtles, whales, and dugongs are all descended from terrestrial ancestors.

○E It is the primary difference between turtles, whales, and dugongs, on the one hand, and pinnipeds, on the other.

3. Select the sentence in the passage in which the author shows that the implication of the common view is contradicted by a new finding.

P2

According to astronomer S.A. Phinney, kicking a rock hard enough to free it from Earth's gravity would require a meteorite capable of making a crater more than 60 miles across.

Moreover, even if Earth rocks were freed by meteorite impact, Mars's orbit is much larger than Earth's, so Phinney estimates that the probability of these rocks hitting Mars is about one-tenth as great as that of Mars's rocks hitting Earth.

To demonstrate this estimate, Phinney used a computer to calculate where 1,000 hypothetical particles would go if ejected from Earth in random directions.

He found that 17 of the 1,000 particles would hit Mars.

4. Which of the following, if true, would cast most doubt on Phinney's estimate of the probability of Earth rocks hitting Mars?

○A Rather than going in random directions, about 25 percent of all particles ejected from Earth go in the same direction into space.

○B Approximately 100 meteorites large enough to make a noticeable crater hit the Earth each year.

○C No rocks of Earth origin have been detected on Mars.

○D The velocity of rocks escaping from Earth's gravity is lower than the velocity of meteorites hitting the Earth.

○E No craters more than 60 miles across have been found on Mars.

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