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 drugs
(D) can usually be modified to make them a more effective drug
(E) can usually be modified to make them more effective drugs
這題答案是e
我想請問a的答案哪裡不好 是因為 are able to比較囉唆嗎?還是有其他原因