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?

• AWhether there are insect pests that sometimes reduce feed-corn yields, but against which commonly used insecticides and the genetic modifi cation are equally ineffective  
• BWhether the price that farmers receive for feed corn has remained steady over the past few years  
• CWhether the insecticides typically used on feed corn tend to be more expensive than insecticides typically used on other crops  
• DWhether most of the farmers who tried the genetically modifi ed corn last season applied more insecticide than was actually necessary  
• EWhether, for most farmers who plant feed corn, it is their most profi table crop