[问答] （求问Alex等众神）阅读36套-E13-第1大题-第2小题的困惑 [复制链接]

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发表于 2013-8-24 17:58:21 |只看该作者 |倒序浏览

原文：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.

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.

不能理解为什么选B。

原文不是说 But the recent discovery ... undermines the attempt to explain away ... as due to convergent evolution了吗？那为什么答案又会是B，can be explained by the idea of convergent evolution。