标题: Prep1-97，看答案有疑问 [打印本页] 作者: chuRiver 时间: 2010-3-16 19:51 标题: Prep1-97，看答案有疑问 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, 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
其中 B while at the same time introducing E but at the same time introducing while与but都是表转折的连接词，答案里说E的but..introduing与前面的have improved不能构成并列。为什么B没有这个问题？作者: hughlv 时间: 2010-3-17 15:19
看了半天才反应过来是个SC题。。。