69. Scientists have modified feed corn genetically, increasing its resistance to insect pests. Farmers who tried out the genetically modified corn last season applied less insecticide to their corn fields and still got yields comparable to those they would have gotten with ordinary corn. Ordinary corn seed, however, costs less,
and what these farmers saved on insecticide rarely exceeded their extra costs for seed. Therefore, for most feed-corn farmers, switching to genetically modified seed would be unlikely to increase profits.
Which of the following would it be most useful to know in order to evaluate the argument?
(A) Whether there are insect pests that sometimes reduce feed-corn yields, but against which commonly used insecticides and the genetic modification are equally ineffective
(B) Whether the price that farmers receive for feed corn has remained steady over the past few years
(C) Whether the insecticides typically used on feed corn tend to be more expensive than insecticides typically used on other crops
(D) Whether most of the farmers who tried the genetically modified corn last season applied more insecticide than was actually necessary
(E) Whether, for most farmers who plant feed corn, it is their most profitable crop
答案是D，我选B。feed corn和genetically modified corn价钱应该不一样啊，为啥OG答案说Whether prices of feed corn go up or down affects the comparison groups equally.而且为啥选D我也不理解，希望谁能给我解释一下。万分感谢作者: stoner28 时间: 2012-5-6 08:37
我选的是A，A的意思是有种害虫会使玉米产量减少，为了杀死害虫，所使用的杀虫剂和改良玉米作用就会相互抵消。
OG解释里面说，it does not matter to the argument whether there are pests against which pesticides and genetic resistance are equally ineffective, because that is compatible with there being pests against which they are not equally effective.
我还是不明为哈A是错的，OG解释的后半句because 。。。。看不太懂。请大家指教。谢谢。
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