旧prep Q21 求解

lealuna

Before scientists learned how to make a synthetic growth hormone, removing it painstakingly in
small amounts from the pituitary glands of human cadavers.

(A) scientists learned how to make a synthetic growth hormone, removing it painstakingly
(B) scientists had learned about making a synthetic growth hormone, they had to remove it
painstakingly
(C) scientists learned how to synthesize the growth hormone, it had to be painstakingly removed
(D) learning how to make a synthetic growth hormone, scientists had to remove it painstakingly
(E) learning how to synthesize the growth hormone, it had to be painstakingly removed by scientists  

答案选C 但我没看出来D哪里错了
笔记上说D中的it指代synthetic growth hormone不符合逻辑
但C中的it指代的是growth hormone
这不是一样的吗？！为嘛在C中就符合逻辑了
求高人讲解~~~~~~~~~~~~

lealuna

多谢指导~~~~~~~

小伊YSY

C中it指代growth hormone，但D中it指代synthetic growth hormone。
在懂得如何合成growth hormone之前，科学家们不得不自取growth hormone才对。句意上来说，后半句不可能自取出在未来才产生的synthetic growth hormone。这个是合成出来的，而非天然的。