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标题: GWD-1-Q41一道语法题？这个时态不太明白。。。 [打印本页]

作者: sxs686 时间: 2013-8-22 10:26
标题: GWD-1-Q41一道语法题？这个时态不太明白。。。

Leaching, the recovery of copper from the drainage water of mines, as a method of the extraction of minerals, it was well established as early as the eighteenth century, but until about 25 years ago miners did not realize that bacteria take an active part in the process.

A. as a method of the extraction of minerals, it was well established

B. as a method of the extraction of minerals well established

C. was a well-established method of mineral extraction

D. was a well-established method of extracting mineral that was (C)

E. had been a method of mineral extraction, well established

这个题我知道可以根据-ved修饰关系排除E，但是C中的这个动作难道不是发生在did not realize之前吗？？？？求解释？谢谢了

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