扫描二维码，直接登录
题库 / Prep2007E1-SC-97
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.
while at the same time they have introduced some 100,000 dangerous chemical pollutants, having
while at the same time introducing some 100,000 dangerous chemical pollutants that have
while they have introduced some 100,000 dangerous chemical pollutants at the same time, which have
but introducing some 100,000 dangerous chemical pollutants at the same time that have
but at the same time introducing some 100,000 dangerous chemical pollutants, having
还没有题目讲解（毕出老师会陆续发布对官方考题的解读，请保持关注）。
while doing 这里做伴随状语，伴随是可以把连词补起来的。
a they指代错误
c at the same time 做状语就近修饰，感觉是引入污染和污染unregulated是同时发生的
de 不能用but，因为but必须连接两个句子，当他连接成分的时候一般是省略的现象，这里but doing前面没有和他平行的对象，所以不对
登录 或 注册 后可以参加讨论