PREP2-22题, 看了答案也不明白~~~

22.        (28162-!-item-!-188;#058&003858)

Herbicides allow cereal crops to be grown very efficiently, with virtually no competition from weeds.  In Britain, partridge populations have been steadily decreasing since herbicide use became widespread.  Some environmentalists claim that these birds, which live in and around cereal crop fields, are being poisoned by the herbicides.  However, tests show no more than trace quantities of herbicides in partridges on herbicide-treated land.  Therefore, something other than herbicide use must be responsible for the population decrease.

Which of the following, if true about Britain, most seriously weakens the argument?

(A) The elimination of certain weeds from cereal crop fields has reduced the population of the small insects that live on those weeds and that form a major part of partridge chicks' diet.

(B) Since partridges are valued as game birds, records of their population are more carefully kept than those for many other birds.

(C) Some of the weeds that are eliminated from cereal crop fields by herbicides are much smaller than the crop plants themselves and would have no negative effect on crop yield if they were allowed to grow.

(D) Birds other than partridges that live in or around cereal crop fields have also been suffering population declines.

(E) The toxins contained in herbicides typically used on cereal crops can be readily identified in the tissues of animals that have ingested them.

答案是A. 我选了D.

我觉得A明明是在support题目中的argument. 因为题中说:Therefore, something other than herbicide use must be responsible for the population decrease. 而A项正好提出了一个他因.

请大家指点.

请大牛指导一下啊！

题干：Herbicides 抑制了weeds的生长

A。weeds的减少导致了以这些weeds为食的小昆虫的减少，从而又导致了以小昆虫为食的partridge的减少。

所以，最终是Herbicides引起partridge的减少。所以A 减弱了题中由其他原因导致partridge减少的论断。

D。其他动物数量减少并不能说明是Herbicides引起partridge的减少，无关选项。