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题库 / Prep2007E2-SC-21
Before scientists learned how to make a synthetic growth hormone, removing it painstakingly in small amounts from the pituitary glands of human cadavers.
scientists learned how to make a synthetic growth hormone, removing it painstakingly
scientists had learned about making a synthetic growth hormone, they had to remove it painstakingly
scientists learned how to synthesize the growth hormone, it had to be painstakingly removed
learning how to make a synthetic growth hormone, scientists had to remove it painstakingly
learning how to synthesize the growth hormone, it had to be painstakingly removed by scientists
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1. E：句子开头是learning，由此可见主句的主语应该是人scientists，而E选项中主句的主语是it，因此排除E；
2. B：Before 从句的时态是过去完成时态，而句子中没有表示过去的过去的时态词。排除B；
3. A：A选项使得整个句子不是个independent 句子，排除A;
4. D：remove it中it指代的是a synthetic growth hormone，但根据句子意思可知应该是remove 人体中的growth hormone，而不是synthetic growth hormone。此外remove这个动作的发出者应该是doctor，而不是scientists。由此排除D。
做题时多注意句子的逻辑意思。
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