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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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C & D 主要是弄清指代问题
C: scientists learned how to synthesize the growth hormone, it had to be painstakingly removed
这里的it指的就是前面的the growth hormone
D: learning how to make a synthetic growth hormone, scientists had to remove it painstakingly
这里的it离得太远，且指代的是a synthetic growth hormone，句意就变成了“在科学家们学会如何制造合成荷尔蒙之前，他们只能将这种合成荷尔蒙从...中提取”，而本意不是提取合成荷尔蒙，而是最开始只能提取荷尔蒙，后来学会了合成荷尔蒙，句意！
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