求教prep2-22

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.

no more than 在这里是什么意思？ 偶看不懂，到底是不是鸟没有被毒死阿

no more than trace quantities 的重点在于"trace", 也就是说在鸟身上发现的毒素只是微量的. 这个证据用来支持something other than herbicide use must be responsible for the population decrease 这个结论.

但是这个结论其实是过分地generalized, 发现的毒素很少, 最多只能证明鸟不是被毒死的, 并不能证明鸟的减少和herbicide没有关系. 答案A就是提供了一种解释, 说明鸟虽然不是被herbicide毒死的, 但是却和herbicide有关, 因此weaken了"something other than herbicide"导致鸟减少的结论.

no more than 在这里是什么意思？

- 不高于

偶看不懂，到底是不是鸟没有被毒死阿

- 鸟的是死了（在讨论是不是除草剂毒死的）

herbicide让weed消失了，靠这种weed生存的chongchong少了，小鸟没得吃了，数量少了

answer a

"trace" mean small quantity. no more than trace means very small quantity.