问题
选择题
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
答案
答案：C
考查虚拟语气。根据句意可知考查与过去事实相反的虚拟语气，故从句用had + v-ed，had Bob walked farther =" if" Bob had walked farther，选C。