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标题: 求助GWD TN 18 28 [打印本页]

作者: bdsjb116 时间: 2010-9-17 16:36
标题: 求助GWD TN 18 28
28: GWD-29-Q9

Manatees, aquatic mammals inhabiting Florida

’s rivers and coastal waters, swim close to the surface and are frequently killed in collisions with boats.To address the problem, boat traffic in manatee-populated waters is being required to maintain very low speeds.Unfortunately, manatees are unable to hear low-pitched sounds and a boat’s sound lowers in pitch as the boat slows.Therefore, this approach may in fact make things worse rather than better.

Which of the following, if true, casts most doubt on the conclusion?

A.The areas where boats would have to maintain low speeds were decided partly on the basis of manatee-population estimates and partly from numbers of reported collisions between manatees and boats.

B.Because the water hyacinth that manatees feed on grows best in water that is nearly still, water hyacinth beds can be disturbed or damaged by fast-moving boat traffic.

C.Over the last several decades, boat traffic in Florida

’s coastal waters has been increasing almost continuously and now represents the greatest threat to the endangered manatee population.

D.The sound of a boat engine generally travels much further under water than it does through the air.

E.When experimenters exposed manatees to the recorded sounds of boats moving at various speeds, the creatures were unable to discern the sounds over normal background noise.

我选的D 答案是E。请NN解释下思路谢谢

作者: hermanchang 时间: 2010-9-17 21:32
D说的是声音在两者中比较，这个没有围绕Manatees对声音的反应说。E很好地弥补了这个gap。ABC都不沾边。

作者: wangziwei 时间: 2010-9-17 22:31
本文的推理是：由于发动机声音变小，M听不见---------》使M更容易发生意外
问削弱
D这种声音在水中比空气中传的远------》对结论无影响，两个比较方在原文没有提及，无关选项，或者你这么想，就算你在水中传的近，反正M也听不见，该出意外还是会出意外
E发动机以任何速度发出的声音，M都听不见-------》从而推翻原文推论过程，即由于声音小听不见，导致悲剧，并且推翻结论，既然声音大小无所谓，那也就不存在因为发动机声音小会比发动机声音大更易产生悲剧的结论
不知道我这么说，你能否明白

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