PREP 逻辑22！！！大家帮忙看下！

vivianxiong

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 seriouslyweakensthe 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.

正确答案：A
我不明白为什么会和 The elimination of certain weeds 有关呢？

Jessielynn

原文说肯定不会是除草剂造成的
要削弱，就是要说明是它造成的，A说杂草少了，生活在草上的昆虫少了，鸟就没食物了，说明除草剂对鸟有间接影响

vivianxiong

原文说肯定不会是除草剂造成的
要削弱，就是要说明是它造成的，A说杂草少了，生活在草上的昆虫少了，鸟就没食物了，说明除草剂对鸟有间接影响

-- by 会员 Jessielynn (2010/9/15 19:24:49)

恩！明白啦~谢谢！！！

emmayuan

那D为什么不对呢

zuhause

因为D扯到了其他鸟，就是显然的干扰项啦~