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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.
题目版答案是A，详解版答案是D，请问到底该选什么？我认为D是排除他因，而详解版中说“A支持说明为什么是UV-B而不是其他原因”，但是本题argument似乎是臭氧层受损导致两栖动物减少，关于UV-B的那些解释只是具体说明这个现像，与最终结论无关吧？期待高人指点 | 
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发表于 2009-10-13 13:49:00
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