问题
选择题
What would have happened＿＿＿＿, as far as the river bank?
A．if Bob has walked farther
B．if Bob should walk farther
C．had Bob walked farther
D．if Bob walked farther
答案
答案：C
此题表示与过去事实相反的假设，主句用would have done,从句用had done,此处用了倒装的省略形式,即省去if, had提到句首。