What would have happened ,as far as 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：D 中少了had，这是是虚拟语气，相当于省略了If的条件状语从句。