请教！prep-2-134

惠灵顿

If a drug that is already on the market has the potential to help adults and children who have the same disease, or if it is widely used in children and the absence of labeling seems dangerous, the FDA can require that the drug undergo pediatric study.

(A) that the drug undergo

(B) that the drug undergoes

(C) that the drug is to undergo

(D) the drug undergoing

(E) the drug to have to undergo

再次向高手请教，这倒题正确选项是A，我选了B，我认为the drug是单数啊，应该用undergoes吧？？？指点指点！！

AlienX

require/order/demand/mandate that之後用subjunctive mood.