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.
本题答案给的是A，但是在解释时却变成了C。请大侠们帮忙看看，到底是A还是C？我选的是A。因为C也算支持吧，排除了“栖息地变小”这一可能导致爬行动物种群下降的原因啊。作者: cherryserena 时间: 2011-9-22 21:23
A) is irelevant. it doesnt explain if UV-B is the reason for the population decline. damage the genes is different from population decline...
D) strengthen the conclusion. it eliminates another possible reason that could explain the ppl decline. if natural habitat shrank => ppl decline.作者: Rachel夏夕空 时间: 2011-10-7 21:27
谢谢楼上几位呀！
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