本贴相关题目 GMATPrep-2007E2-SC-21 (VAQB)

00:00:00

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

Ascientists learned how to make a synthetic growth hormone, removing it painstakingly
Bscientists had learned about making a synthetic growth hormone, they had to remove it painstakingly
Cscientists learned how to synthesize the growth hormone, it had to be painstakingly removed
Dlearning how to make a synthetic growth hormone, scientists had to remove it painstakingly
Elearning how to synthesize the growth hormone, it had to be painstakingly removed by scientists

正确答案: C

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witness236

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发表于 2012-4-22 17:24:38 | 只看该作者回帖奖励

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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
(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
这道题给出的答案是C，我想知道D选项有什么问题