GWD 1-41

braveMBA

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.

1. as a method of the extraction of minerals, it was well established
2. as a method of the extraction of minerals well established
3. was a well-established method of mineral extraction

4. was a well-established method of extracting mineral that was
5. had been a method of mineral extraction, well established

Why not E?

sammen

E 1时态,这里没有很明显的过去完成的标志或意思.2establied修饰的对象变化了,应该是修饰method的,E变成修饰extraction.

leadership

E:had been a method of mineral extraction, well established
well established修饰extraction了，当然不对

steveyangxt

同意