求助一道题~关于while用法~

nianbohu

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, and have
	but introducing some 100,000 dangerous chemical pollutants at the same time that have
	but at the same time introduce some 100,000 dangerous chemical pollutants, having

答案是B

nianbohu

有道理，谢谢！

xiaoxiaoxxliu

d的另外一个问题是at the same time的位置不对，让人以为所有的污染物引入是同一时间发生的

nianbohu

一语道破天机了一刚~谢啦！

nancy5130

but屬於coordinating conjunction，前後要求嚴格的parallelism。
while屬於subordinating conjunction，對parallelism的要求沒有coordinating conjunction嚴格。

用but的話，have improved和introducing明顯不能平行；所以只能用while;)

stevenckguo

因为语气加强与减弱都是改变句意。本来是不肯定的，变为肯定的，就不同了呀

nianbohu

其它地方我同意，但为啥语气加强，就要排除？

stevenckguo

我的理解：用排除法。一般原句无论结构多混乱， 还是可以看出句子的结构，语义的。D E用but, 把语气加强，排除。

C，无代词优于有代词。they 可以指代methods或者“industrialization and modern methods of...”造成指代不清，排除。

while at the same time是对的，没有意思重复。B中，that have 修饰pollutants；A中having做伴随，修饰整个句子，修饰错误。that 从句优于having done [做定语时]。所以排除A。

PS：未划线部分也是重要线索。未划线的they要和划线中的they 指代同一个先行词。根据句义判断。要是指代不同的名词，则是指代不清。必错！

语法原则: Grammar, Meaning, and Concision.          个人拙见~