不好意思,应大家的建议,把全部备选答案贴出来
Scientists have made genetic modifications to cotton to increase its resistance to insect pests. According to farmer's report, the amount of insecticide needed per acre to control insect pests was only slightly lower for those who tried the modified seed than for those who did not. Therefore, since the modified seed costs more than ordinary seed without producing yields of higher market value, switching to the modified seed would unlikely to benefit most cotton farmers economically.
Which of the following would it be most useful to know in order to evaluate the argument?
A. Whether farmers who tried the modified cotton seed had ever tried growing other crops from genetically modified seed
B. Whether the insecticides typically used on ordinary cotton tend to be more expensive than insecticides typically used on other crops
C. Whether for most farmers who grow cotton it is their primary crop
D. Whether the farmers who have tried the modified seed planted as many acres of cotton, on average, as farmers using the ordinary seed did
E.Whether most of the farmers who tried the modified seed did so because they had previously had to use exceptionally large quantities of insecticide为什么D正确,我理解不来,请大家帮忙了....谢谢!作者: mary1 时间: 2004-9-8 12:38
One fact: scientists are making genetic modifications to increase resistancecause 1: the amount of insecticide was lower for those geneticly modified seed than those originalcause 2: the modifiied seeds cost more and don't have higher market valueEffect: the modified seed isn't beneficial for cotton farmers economically. If we change the evaluating sentence, we could regard it as an assumption for this reasoning: the farmers who have tried the modified seed planted as many acres of cotton, on average, as farmers using the ordinary seed. If we say yes, the reasoing is accetable. If we say no, the reasoning is undermined for the results from the farmers' report is irrelevant.
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