求prep--SC一题

MissZiona

130.
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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

我选C，答案选B。我是想while连接的两部分要尽可能形式对称：have improved...对应have introduced...

请大牛们帮忙，想不通为什么选B！

[此贴子已经被作者于2009/10/10 22:23:33编辑过]

coolboxer

(B) while at the same time introducing some 100,000 dangerous chemical pollutants that have      that 引导定语从句修饰pollutants符合逻辑；introducing 现在分词做伴随状语

(C) while they have introduced some 100,000 dangerous chemical pollutants at the same time, and have    and have 的逻辑主语不对；

MissZiona

以下是引用coolboxer在2009/10/10 22:27:00的发言：

(B) while at the same time introducing some 100,000 dangerous chemical pollutants that have      that 引导定语从句修饰pollutants符合逻辑；introducing 现在分词做伴随状语
                

(C) while they have introduced some 100,000 dangerous chemical pollutants at the same time, and have    and have 的逻辑主语不对；

谢谢boxer！

MissZiona

以下是引用coolboxer在2009/10/10 22:27:00的发言：

(B) while at the same time introducing some 100,000 dangerous chemical pollutants that have      that 引导定语从句修饰pollutants符合逻辑；introducing 现在分词做伴随状语
                

(C) while they have introduced some 100,000 dangerous chemical pollutants at the same time, and have    and have 的逻辑主语不对；

刚突然想到，while不是连词么，它不是应该接句子么，B中while接的是现在分词...

能帮我解释下这点么？