问题补充：
I my homework yesterday, but unfortunately I forgot about it totally.
A. need have handed in
B. should have handed in
C. must have handed in
D. may have handed in
答案：
A. need have handed in
(答案→)B. should have handed in
C. must have handed in
D. may have handed in
解析：考查虚拟语气。But后面的句子使用陈述语气，前面的句子使用虚拟语气。本题But后面的句子使用了过去时，故前面的句子是与过去事实相反的虚拟语气。need have done需要做某事，实际上却没有做；should have done本应该做某事，实际上却未做；must have done一定做了某事（表示推测）；may have done也许做了某事（表示推测）；句意：我本应该昨天交作业，但是不幸的是我完全忘记了。
