What would have happened ，as far as up to the river bank.
A. Bob had walked farther
B. if Bob should walk farther
C. had Bob walked farther
D. if Bob walked farther
网友回答
A. Bob had walked farther
B. if Bob should walk farther
(答案→)C. had Bob walked farther
D. if Bob walked farther
解析：
因为主句的谓语动词用了would have happened，所以从句的谓语动词要用过去完成时。在虚拟语气中，如果条件状语从句中的if省略，该句要倒装。