请教大家,我对时间状语从句省略结构不是很清楚,特别是涉及到while的用法。以下举了两例请大家帮忙分析一下。谢谢!!!
PREP 19. 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
ANS: B
大全95题: Although some officials noted that using machines for farming in
(A) mechanization of farming in the
(B) mechanization of farming in the
ANS:B
置顶贴里有详细的解答,
http://forum.chasedream.com/dispbbs.asp?boardID=23&ID=81945&page=1
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