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题库 / Prep2008E2-SC-196
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.
as a method of the extraction of minerals, it was well established
as a method of the extraction of minerals well established
was a well-established method of mineral extraction
was a well-established method of extracting mineral that was
had been a method of mineral extraction, well established
请看讲解视频
A 双主语
B 缺少谓语动词
C 正确
D that was无论是指代method还是mineral都使得后面的as early as变成从句的成分，那就变成了method（或者mineral）was as early as the eighteenth century，显然说不通。
E 时态不对，过去完成时表示leaching是过去的办法，现在不用了，但句中并没有表述这种意思
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