问题补充：
What a kind teacher. But for his help, I my study.
A. wouldn’t finish
B. wouldn’t have finished
C. shouldn’t have finished
D. mustn’t have finished
答案：
A. wouldn’t finish
(答案→)B. wouldn’t have finished
C. shouldn’t have finished
D. mustn’t have finished
解析：句意：多么好的老师，要不是她的帮助，我不可能完成学业。but for是“要不是”的意思。后面的主句要用虚拟语气，根据句意是是对过去的虚拟，所以用：would have done所以选B.
