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
(A) 整个句子中的两个代的是pollutants；having gone…分词结构有作伴随状语修饰have introduced的歧义，而不是作代词they指代对象不一致，划线部分they没有指代对象，未划线部分的they指 pollutants的定语。 (B)正确 (D) but + 现在分词的用法错