问题补充:
I wrote a letter to John for his help during my high school years,without which I the college entrance exam.
A. would fail
B. would have failed
C. should fail
D. must have failed
答案:
A. would fail
(答案→)B. would have failed
C. should fail
D. must have failed
解析:B考察虚拟语气,句义:我给John写了一封信,感谢他在高中给我的帮助,没有他的帮助,我不会通过高考的。句义可知,这是对过去情况的假设,所以主句使用情态动词+have done的形式。故B正确。