gwd-1-41看过贴，有争论，所以还是不确定

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

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

给的答案是C，但也有不少人支持E，反对E的是说没有必要用过去完成时，那eighteenth century明显在25 years ago之前，就是该用过去完

成时嘛

这道题我刚做， 我是觉得 E的 过去完成时不对   后面已经有了明确的时间  as early as the eighteenth century。 如果一道题 直接写  in the eighteenth century，前面的动词就肯定是一般过去时了，   一般无故把一般过去时改过去完成时都算错，好像是这么着的。

再说了， c 比 e 来的简洁， e 就是 一个 n. + 分词结构（修饰形容前面的n.）  而c 直接把 分词结构化成 adj. 放在n前，没有造成歧义

如错，请指正。

不好意思，没明白楼上的意思。

Leaching,  ..., it was well established  

但是原文本身 well established就是修饰 leaching的呀， 只是主语重复了，肯定错。 那 C 把 well-established直接放在 method前， 修饰 method。

如果照你的说法，那反而应该是 E 对了，不懂ing

不要阿，cairol一说，我又糊涂了，怎么办？？？？？？

没明白过来。 能说具体一点吗？ well establish应该修是什么呢？

另外，有一道 我选了C，也是过去完成时，我是没觉得 d选项中， 把动词部分变成分词结构 成了修饰成分 这样是对的。

Q20:

In the mid-1970’s, since birds were overcome by pollution, and routinely falling from the sky above Los Angeles freeways, this prompted officials in California to devise a plan that reduced automobile emissions.

1. since birds were overcome by pollution, and routinely falling from the sky above Los Angeles freeways, this prompted officials in California to devise a plan that reduced
2. since birds that had been overcome by pollution were routinely falling from the sky above Los Angeles freeways, it prompted officials in California to devise a plan that would reduce
3. birds had been overcome by pollution and routinely fell from the sky above Los Angeles freeways, prompting officials in California to devise a plan that reduced
4. birds overcome by pollution routinely fell from the sky above Los Angeles freeways, prompting officials in California to devise a plan to reduce

5. birds overcome by pollution and routinely falling from the sky above Los Angeles freeways were prompting officials in California to devise a plan to reduce

   Answer:

Q20我是这样看的，C里面过去完成时和一般现在时不能并列。

我做这道题，看题干就知道是考分词表结果，确定到C和D，然后C并列不对，就选D。

从逻辑意思看，应该是well established修饰method，是一种很成熟的方法，而不能说leaching本身是well established。E中well established分词短语修饰leaching，所以错。