大全984答案有歧义！

1.       There is ample evidence, derived from the lore of traditional folk medicine, that naturally occurring antibiotics are usually able to be modified to make them a more effective drug.

(A) are usually able to be modified to make them a more effective drug

(B) are usually able to be modified to make them more effective drugs

(C) are usually able to be modified, which makes them more effective drug

(D) can usually be modified to make them a more effective drug（E）

(E) can usually be modified to make them more effective drugs

大全给出的答案E中more effective drugs有歧义：是more drugs还是more effective?我感觉D更好，请大家确认下。

这里them不是指代drugs，是指代antibiotics.

them
   a more effective drug

不一致

代词指代和主谓是要求单复数一致的，这里make sth sth结构一定要求单复数一致么？

make them a more effective drug理解为“把他们做成一种更有效的药物”，为什么一定是“把他们做成各种更有效的药物”？

一种更有效的药物:  a/one kind of drug but not a drug

a drug = a medicine   or   a substance for making medicines