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: angelsgx 时间: 2011-6-13 19:36
题目说：农民去年尝试了改良基因的玉米，他们在农药上节省下来的钱和买
这种种子多花的钱差不多，所以说，换改良玉米给农民不会增加利润。
问以下哪点对判断结论最有用
d: 农民是否在改良基因的玉米上面多用了农药， 如果是，那事实上他们以后
可以少用农药，那么就可以节省更多的钱，题目中的结论就不成立
b。玉米前几年的价格是否稳定 这个和题目不相关，因为题目结论建立的基础
在于农药花的钱和种子花的钱作比较，改良基因玉米和普通玉米作比较，不涉
及到玉米价格作者: yayajiaojef 时间: 2011-6-15 06:34
解释得很清楚。。明白了，非常感谢哦作者: zhangluE 时间: 2011-6-18 08:29
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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