求助一个prep语法题

克瑞斯

Industrialization and modern methods ofinsect control have improved the standard of living around the globe whileat the same time they have introduced some 100,000 dangerous chemicalpollutants, having gone virtually unregulated since they weredeveloped 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

这题做的时候觉得没有靠谱的选项，勉强选了A ,
A,having有问题
B,introducing 有问题，就算和主句一致而省略主谓，也应该是（have） introduced 吧？
C, at the same time的位置和which指代有问题
D,E introducing和主句谓语无法并列

请各位指点，谢过了~~

SCFFGMAT

B的话 while+现在分词 表示与此同时的意思  A的话首先THEY的指代就有问题了。

克瑞斯

SCFFGMAT 发表于 2015-9-24 22:00
B的话 while+现在分词 表示与此同时的意思  A的话首先THEY的指代就有问题了。

明白了感谢