11. 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. scientist learned how to synthesize合成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 have to be painstakingly removed by scientists

给的答案是C，我认为是D。因为我觉得主动优于被动。大家看呢？

这个题目我第一遍也选的D，但是现在觉得C比D好

感觉D的含义和C不同
D是说－科学家在学习合成hormone之前要先做另外一件事，没体现出原题的意思

不知对不对，请NN指点～！