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Before scientists learned how tomake a synthetic growth hormone, removing it painstakingly in small amountsfrom the pituitary glands of human cadavers. (A) scientists learned how to makea synthetic growth hormone, removing it painstakingly (B) scientists had learned aboutmaking a synthetic growth hormone, they had to remove it painstakingly (C) scientists learned how tosynthesize the growth hormone, it had to be painstakingly removed (D) learning how to make asynthetic growth hormone, scientists had to remove it painstakingly (E) learning how to synthesize thegrowth hormone, it had to be painstakingly removed by scientists
A错在句子不完整是个fragment B错在动作的先后顺序，learn这个动作发生在remove之后，用过去完成时不恰当 C正确答案 D我看gmatclub上的人解释说是代词it指代 hormone错误，这里我就费解了，为什么C中it指代hormone没错但是D错了 E错在modifier修饰了it，应该修饰scientists.
请NN帮我看看D为啥错，谢谢
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发表于 2016-9-26 17:50:54
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