求NN解答一道prep题目！关于while的用法

Lizzy233 · 发表于 2014-9-17 11:06:11

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

这道题选B，能每个选项解释一下吗？
while和at the same time不是语义重复吗？GMAT中while的用法是比较偏向同时发生的意思吗？while doing和前面的不平行啊~为什么

暴躁的大叔 · 发表于 2014-9-17 16:16:01

while的用法是偏向比较的含义，和 at the same time不存在重复

这里正确选项B while doing是做伴随状语，主语跟主句主语一样，伴随状语不需要平行啊。

lemon123 · 发表于 2014-9-23 15:24:01

while doing偏向比较主句与从句动作之间的不同（在主语相同情况下）。很明显这里是想比较improve和introduce，无论前面improve是用什么时态

求NN解答一道prep题目！关于while的用法

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