贴一道我今天做狒狒的错题,请大家帮我分析一下我的思路。 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.
后来看了cd上的讨论贴才知道,这个题目答案有些争议。我当时选的是D,狒狒给出的答案是A,但狒狒详解给出的答案是D。经过后来的分析,我现在认为A更符合题意要求。 我当时做题的思路是:A加强,因为这排除了非UV-B 导致amphibians数量减少的可能性。D无关,因为栖息地变小与the depletion of the ozone layer没有关系。 后来终于弄明白,A无关,因为只要证明the depletion of the ozone layer和amphibians数量减少的关系就可以,至于是否一定是因为UV-B 导致的倒无所谓。换言之,如果A取反,除了UV-B, the ozone layer还可以阻挡别的伤害基因的物质,那the depletion of the ozone layer也一样可以导致amphibians数量减少。所以,A正确与否不影响文中的结论。 D是排他加强,就是说数量减少不是因为栖息地减少引起的,所以增加了是因为the depletion of the ozone layer引起的可能性,所以加强。 |