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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
either of these two interpretations leads to an absurd sentence -- neither the method (= NOUN1) nor the mineral (= NOUN2) "was as early as the 18th century" -- so this option is flat-out incorrect. from Ron about why D is incorrect
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