OG12 CR69

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