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

 选c 怎么可能？？

 我选d。。。

 who can help me?? thanks a lot

(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

==》体会一下意思，原句是synthesize  hormone 还是make hormone ?

不是吧...我还是觉得D好~~~大家讨论一下~~~

个人觉得D好。

C的it指代容易产生歧义。如果按照就近指代的原则，it应指代合成的荷尔蒙，而合成的荷尔蒙怎么能从死人尸体中取得呢？逻辑意思不对。