一、用“情态动词＋have ＋done”结构表示对过去动作的推测

1．must have done： 表示对过去动作的肯定推测，常译作“一定……”，只能用于肯定句中。其否定形式为can’t／couldn’t have done 疑问式为Can／Could...have done﹖。
could ／might have done：表示对过去发生的动作的可能性推测，常译作“可能……”。如：
1) Sorry I’m late． I _____have turned off the alarm clock and gone back to sleep again． (北京 2000春)
A． might B． should C． can     D． will
选A 表示可能性 自己也不确切
2) He _____ have completed his work; otherwise, he wouldn’t be enjoying himself by the seaside.
（北京2005）
A. should B. must C. wouldn’t D. can’t
选B
2．should have done ／ ought to have done：表示过去本应该做某事而实际上没有做。
should not have done ／ ought not to have done：表示过去本不应该做某事但事实上却做了。
need have done：表示过去本来有必要去做某事，但事实上没有做。
need not have done：表示过去本来没有必要做某事，但事实上却做了。如：
1) I was really anxious about you． You _____home without a word． (NMET2001)
A． mustn’t leave           B． shouldn’t have left
C． couldn’t have left      D． needn’t leave
选B
2) I told Sally how to get here, but perhaps I ____for her． (NMET’94)
A． had to write it out         B． must have written it out
C． should have written it out   D． ought to write it out
选C
二、考查情态动词基本用法之间的比较和辨析。借助语境来考查考生对那些最常见的情态动词的基本用法的理解和掌握。
1) —Is John coming by train﹖
—He should, but he _____not． He likes driving his car． (NMET2002)
A． must B． can C． need D． may
选D
2) —I hear you’ve got a set of valuable Australian coins． ______I have a look﹖
—Yes, certainly． (北京2002春)
A． Do B． May C． Shall D． Should
选B
3) Mr. Bush is on time for everything． How ＿＿＿＿ it be that he was late for the opening ceremony﹖ (上海2001春)
A． can B． should C． may D． must
选A
4) John, look at the time. _____you play the piano at such a late hour? （全国III 2005）
A． Must B． Can C． May D． Need
选A 基本用法 表示一定 也可译为非得
5）—Are you coming to Jeff’s party﹖
—I’m not sure． I ___go to the concert instead． (NMET2000)
A． must B． would C． should D． might
选D 又如：
I should have been there, but I ____not find the time． (上海2000春)
A． would     B． could    C． might     D． should
选B
6) Johnny, you _____play with the knife, you _______hurt yourself． (NMET’96)
A． won’t; can’t   B． mustn’t; may
C． shouldn’t; must      D． can’t; shouldn’t
选B 第一空表示一定不要 第二空表示可能性
7) —Will you stay for lunch﹖
—Sorry, ____． My brother is coming to see me． (NMET’99)
A． I mustn’t      B． I can’t    C． I needn’t    D． I won’t
选B 不能
8）Tom , you ______leave all your clothes on the floor like this ! （全国I,II 2005）
A． wouldn’t B． mustn’t C． needn’t D． may not
选B 表示责备
9)—When can I come for the photos﹖ I need them tomorrow afternoon．
—They _____be ready by 12：00． (NMET’98)
A． can B． should C． might D． need
选B 表示估计
10) Helen ______ go on the trip with us, but she isn’t quite sure yet. (安徽 2005)
A. shall B. must C. may D. can
选C