GWD 一道考古，不确定答案

GWD-24-29.
Plant scientists have been able to genetically engineer vegetable seeds to produce crops that are highly resistant to insect damage. Although these seeds currently cost more than conventional seeds, their cost is likely to decline. Moreover, farmers planting them can use far less pesticide, and most consumers prefer vegetables grown with less pesticide, therefore, for crops for which these seeds can be developed, 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
B. Whether farmers typically use agricultural pesticides in larger amounts than is necessary to prevent crop damage.
C. Whether plants grown from the new genetically engineered seeds can be kept completely free of insect damage.
D. Whether seeds genetically engineered to produce insect-resistant crops generate significantly lower per acre crop yields than do currently used seeds.
E. Whether most varieties of crops currently grown commercially have greater natural resistance to insect damage than did similar varieties in the past.

感觉应该是B，但是答案是D。

觉得一直谈pesticide，B的话，如果farmers确实用力比唱规的量多的pesticide，那么这个基因产品的优势就不明显，因为这个基因产品本身并不能完全不用杀冲剂，只是想对现在的庄稼用得少很多。

求解释。