英语中的一种特殊虚拟语气形式

"情态动词＋不定式完成体"是英语中表示过去的一种特殊虚拟语气形式，它通常表示过去的可能性、过去本该发生而未发生或不需要发生却又发生了的事情以及对过去发生的事情表示推测、肯定等。
1"m ust ＋have ＋过去分词"表示对过去事情肯定性的推测。
【例】
It must have been this obvious aimlessness that led to my downfall．
一定是这种明显的毫无目的（的游逛）使我倒了霉。
And my father must have been hurt too a little．
父亲心里肯定也有点不好受。
【题】
Mary's score on the test is the highest in her class．She _____have studied very hard．
A）may
B）should
C）must
D）ought to（答案为C）
2"could／may／might ＋have ＋过去分词"表示对过去事情的可能性推测。
【例】
It may have rained last night，but I'm not sure．
昨晚可能下过雨，但我不能肯定。
The cause of the fire could have been cigarette-end．
可能是烟头导致起火的。
Your father might have caught the last train．
你父亲也许赶上了末班火车。
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3"should／ought to ＋have ＋过去分词"表示过去本该发生的事情，但由于某种原因并没有发生。
【例】In a rush all the rage I should have felt for my attackers was directed against those contented people standing in front of their warm，cozy homes talking about all theguns they were going to buy．当时我一气之下，把本该对袭击者怀有的满腔怒火，全都发泄到这些心满意足、站在自己的温暖舒适的安乐窝前谈论着买什么样枪支的人身上了。
Presumably that I should have looked out-raged．．．
大概我本该显出愤愤不平的样子……
He went on saying something about"ought to have got here at seven o'clock，but-"他还在往下说，说什么"本该七点钟到这里，但是--"
4"could／should／might ＋have ＋过去分词"还可用来表示委婉地提出批评、看法或建议。
【例】"You could have been a bit more helpful when we arrested you，"he said to mereproachfully．他带着责备的口气对我说，"我们抓你的时候，你本可以稍微帮点忙的。"
Say，you oughtn'tto have driven away those kids．嗨，你不应该把那些孩子赶跑。
【题】
With all this work on hand，he _____ to the cinema last night．
A）mustn't go
B）wouldn't go
C）oughtn't to go
D）shouldn't have gone（答案为D）
Tom_____ better than to ask Dick for help．
A）shall know
B）shouldn't know
C）has known
D）should have known（答案为D）
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5"needn't ＋have ＋过去分词"表示过去发生了不必要发生的事情。
【例】
You needn't have said that．你其实用不着说这话。
They needn't have got up so early．他们用不着起那么早。
【题】
You _____all those calculations！ We have a computer to do that sort of thing．
A）needn't have done
B）must not have done
C）shouldn't
D）can not have（答案为A）
You _____the class to tell me that，you could have come up to me afterwards．
A）needn't have interrupted
B）needn't interrupt
C）needn't to have interrupted
D）needn't to interrupt（答案为A）
I _____to him because he phoned me shortly afterwards．
A）ought to have written
B）can have written
C）couldn'thavewritten
D）needn't have written（答案为D）