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 ANSWER: B MINE: A 做题的时候只在AC间徘徊,因为觉得have improved... while... have introduced是句子的并列谓语。 但后来又觉得A项和B项最后用having 和which have都不能准确的修饰chemical pullutants。还是B的that have最perfect。但是B项中的introducing是什么成分,难道它的执行者不是Industrializations and modern methods吗? Confused了! 请NN们指教! |