GWD 1-41

JEANINDE

GWD 1-41

Q41:

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

Why not E?

trojanlove

不知道是否可以这样解释：Well established here modifies method instead of Leaching.

天使与海豚

E的时态不对吧。。。

marcovios

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

well established修饰extraction了，当然不对

wallencechen

同上