Fact: We now have insect resistant seed.
Premise: These seeds currently cost more but their cost is likely to decline.
Premise: Farmers can use far less pesticide.
Premise: Consumers prefer vegetables grown with less pesticide.
Conclusion: For crops for which these seeds are available their use is likely to become the norm.
Which of the following would be most useful to know in evaluating the argument above?
A)Whether plant scientists have developed insect-resistant seeds for every crop that is currently grown commercially?
No need for evaluating this argument. For this argument is only applicable for crops for which these seeds are available.
B)Whether farmers typically use agricultural pesticides in large amounts than is necessary to prevent crop damage?
This is useful. Because if farmers have been using unnecessarily large amount of pesticide then the use of such seeds would likely to be less economical then to educate the farmers to NOT use large amount of pesticide. The later will solve all problems without have to resort to the insect resistant seeds and lend the argument to its failure.
C)Whether plants grown from the new genetically engineered seeds can be kept completely free of insect damage?
As long as it keeps most of the insect away, even if it's not completely free of insect damage the argument still stands.
D)Whether seeds genetically engineered to produce insect-resistant crops generate significantly lower per acre crop yields than do currently used seeds?
This is talking about cost. One of the premise already said that it is currently costly. So this would not bring any new info into the understanding of the issue. As long as the cost can be lowered sufficiently in the future this is not going to be a problem for the insect resistant seeds to become the future norm.
E)Whether most varieties of crops currently grown commercially have greater natural resistance to insect damage than did similar varieties in the past.
Kind of irrelevant, don't you think?
So my choice would be B.
Keep on asking, and it will be given you;
keep on seeking, and you will find;
keep on knocking, and it will be opened to you.