(2013·新课标Ⅰ,32)There's no way of knowing why one man makes an important discovery another man,also intelligent,fails.
A. since
B. if
C. as
D. while
网友回答
A. since
B. if
C. as
(答案→)D. while
解析:并列连词。根据句意,前后两句话为两种情况的对比“一个人会做出一个重要的发现,而另一个人,也很聪明,但是失败了”。并列连词while表示对比。故选D。