急求PREP SC一题解答牛人来LOOK

zlljolie · 发表于 2011-7-9 13:12:07

Industrialization and modern methods of insect control have improved the standard of living around the globe while at the same time they have introduced some 100,000 dangerous chemical pollutants, having gone virtually unregulated since they were developed more than 50 years ago.

(A) while at the same time they have introduced some 100,000 dangerous chemical pollutants, having

(B) while at the same time introducing some 100,000 dangerous chemical pollutants that have

(C) while they have introduced some 100,000 dangerous chemical pollutants at the same time, which have

(D) but introducing some 100,000 dangerous chemical pollutants at the same time that have

(E) but at the same time introducing some 100,000 dangerous chemical pollutants, having

这题正确选项B。为什么A、C不对呢？
A中的, having，我记得完成时的现在分词不可以作限制性修饰语，但可以做非限制修饰语啊，这里不可以理解成, having
修饰前面的pollutants吗？
C的话，非限制定从,which have哪里错了吗？

一直觉得B中while(they are) introducing也不对啊。。。while表对比，从语意上看，主从都用完成时态have done才对啊！

牛人解答

lhnstefsun · 发表于 2011-7-9 15:57:15

首先having可以修饰前面的pollutants但也可以表伴随，所以为了不产生歧义，在这种确定修饰前面的先行词的情况下，用定语从句直接修饰最好，另外在一句话中出现的代词只能指代一个东西不能前面出现的they指代A而后面的they指代B，也是为了不要出现指代不清的问题。像A和C中都用了，they have introduced容易和句子结尾处的they发生指代不清的情况，所以A、C是错误的。
还有楼主说的时态问题，楼主补充的while(they are) introducing和while doing是不一样的，while doing的doing是非谓语动词修饰前面的句子，表示和前面的句子同时发生，并不是楼主想的时态不一致。

本贴相关题目 GMATPrep-2007E1-SC-97 | TN-23-SC-21 (OCTR)

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