What would have happen___,as far as the river bank?

问题描述:

What would have happen___,as far as the river bank?
5.What would have happened______,as far as the river bank?(2001上海)
A.Bob had walked farther B.if Bob should walk farther
C.had Bob walked farther D.if Bob walked farther
为什么答案选C,希望得到详细解析.

C.had Bob walked farther
倒装,= if Bob had walked farther
表示与过去事实相反,所以用had walked