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 这题答案为B. PREP 的解释是说,while在这里表示的是与。。同时的意思,同时也是原文要表达的意思从而否定了DE. 我的疑问在于,如果while表达的是与。。同时,岂不是和at the same time 语意重复?我觉得这里while应该表达的是转折。不知道我的想法对不对