请教prep的一道sc

tedpgsps

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

 这道题问什么要选A呢，B和D都有什么问题呢？

mych666666

require that...从句，要用省略的虚拟语气，即require that...do sth.用动词原型undergo

tedpgsps

谢啦！