PREP关于非谓语的一个题 救命呀

呼啸700

21.(25520-!-item-!-188;#058&002357)

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(答案)

(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

D 选项 为什么不好呀 是不是  before doing  本身就是不好呀  牛牛们 帮我解释一下 谢谢

cycyang

(D) learning how to make a synthetic growth hormone, scientists had to remove it painstakingly
如果选此项，则说明painstakingly的承受者是scientists, 而不是patients. 与事实不符。

GmatMakeIt

现在分词做伴随表示一直进行，这里两个动作有时间先后吧

geegee

a:不成一句。
learning的话表示伴随，before放在前面读上去不顺，这句的重点不是scientists,而是荷尔蒙怎样怎样。painstakingly表示工作费力，倒是可以用的。个人的意见。