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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.
为什么d 不能选呢？a 确实不能有strengthen 的作用，但我认为d 也不能增强，说amphibians 的栖息地在上个世纪没有变小，（哦，我明白了，这相当于是一个假设，正因为它的 栖息地 没有变小，才可以看出是因为ozone 减少导致amphibians 的减少，对吗？） | 
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发表于 2004-7-26 23:11:00
