虚拟语气问题I'm glad I went over all my notes;otherwiseI’m glad I went over all my notes; otherwise _____ . A. I may have failed B. I’d fail C. I’d have failed D. I’ll have failed 答案是C,为什么不是B

虚拟语气问题I'm glad I went over all my notes;otherwise
I’m glad I went over all my notes; otherwise _____ .
A. I may have failed B. I’d fail C. I’d have failed D. I’ll have failed
答案是C,为什么不是B

句子的意思是 我很庆幸我复习了我所有的笔记,
要不然的话我已经不及格.
结果是我已经pass及格了.(相反可能已经不及格了,所以要用完成时)
i'd have failed= I would have failed