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38. Amphibian populations are declining in numbers worldwide. Not coincidentally, the earth’s ozone layer has been continuously depleted throughout the last 50 years. Atmospheric ozone blocks UV-B, a type of ultraviolet radiation that is continuously produced by the sun, and which can damage genes. Because amphibians lack hair, hide, or feathers to shield them, they are particularly vulnerable to UV-B radiation. In addition, their gelatinous eggs lack the protection of leathery or hard shells. Thus, the primary cause of the declining amphibian population is the depletion of the ozone layer. Each of the following, if true, would strengthen the argument EXCEPT: (A) Of the various types of radiation blocked by atmospheric ozone, UV-B is the only type that can damage genes. (B) Amphibian populations are declining far more rapidly than are the populations of nonamphibian species whose tissues and eggs have more natural protection from UV-B. (C) Atmospheric ozone has been significantly depleted above all the areas of the world in which amphibian populations are declining. (D) The natural habitat of amphibians has not become smaller over the past century. (E) Amphibian populations have declined continuously for the last 50 years. 给的答案是A，但是答案解答版的答案说是D，如下是解释 思路：原文论述臭氧层的破坏造成UV-B辐射过量是导致两栖动物数量减少的主要原因。 A：支持说明为什么是UV-B而不是其他原因。 B：支持说明为什么UV-B会降低两栖动物的数量。 C：提供空间论据说明臭氧层受损和两栖动物数量减少的相关性。 D：中性评价。不Weaken也不Strengthen. E：提供时间论据说明臭氧层受损和两栖动物数量减少的相关性。 我的问题是D是典型的排除他因啊，如果D取非－鸟的栖息地少了，鸟的减少就可能并不是因为ozone减少引起的 这样想对不对呢？ | 
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发表于 2008-6-28 02:10:00
