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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.
这道题我在网上找不到解释,看来大家对这题都很明白,但是想了很久还是不明白。我是选D的。 我的疑问在于:这道题 要削弱的是Therefore, something other than herbicide use must be responsible for the population decrease这个结论,如果是的话选A那不是就是说的确有其它原因说明题目中要说的问题吗?要削弱结论就是要加强Some environmentalists 的claim不是吗? 想来想去还是不明白,脑子转不过来,麻烦各位CDER了 |
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