问题
选择题
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
答案
答案：C
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。
