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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.
答案选A， 可是E为什么不对呢？这句herbicidetests show no more than trace quantities of herbicides in partridges on herbicide-treated land.是什么意思呢？谢谢！！
-- by 会员 beryl8 (2010/8/17 21:52:41)
感觉A选项有点牵强。如果是除草剂杀死了小昆虫，partridge因为吃小昆虫而致死，按照选项的逻辑，应该是除草剂通过食物链导致了partridge死亡，那么怎么会“herbicidetests show no more than trace quantities of herbicides in partridges on herbicide-treated land”，关于这点不是很明白，希望NN指点。
-- by 会员 JuggernautZNJ (2010/8/17 22:26:22)
