标题: 问一个关于v-ing的问题。懂语法的进来看看。 [打印本页] 作者: elusive 时间: 2016-4-20 07:03 标题: 问一个关于v-ing的问题。懂语法的进来看看。 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