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（1） should (ought to) have＋过去分词
表示过去应该做而（实际）没有做的事情,含有责备或遗憾的语气，意为“本应该……”；其否定形式为“should not／ought not to have ＋ 过去分词”，表示某种行为不该发生但却发生了。
例：Mr. White _____ at 8:30 for the meeting , but he didn’t’ show up.
A. should have arrived B. should arrive
C. should have had arrived D. should be arriving
（2）needn’t have＋过去分词
表示过去没有必要做某事, 但实际上做了某事。
As you worked late yesterday, you_________ have come this morning.
A. mayn’t B. can’t C. mustn’t D. needn’t
[注意] He didn't need to come yesterday，意为“他昨天没有必要来（实际也没来）”。
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（3）must have＋过去分词
用于肯定句，表示“过去一定做过某事”，表示一种很有把握的推测。其否定形式分别用can’t/ couldn’t和can/ could。例如：
It must have rained last night, for the ground is wet this morning.
昨天晚上一定是下雨了，因为今晨地面是潮湿的。
She didn’t attend the lesson yesterday. She must have been ill.
她昨天没有上课，她一定是生病了。
[注意] 对过去发生情况的否定推测常用can’t／couldn’t have ＋过去分词。
I have lost one of my gloves. I ________ it somewhere .
A. must drop B. must have dropped
C. must be dropping D. must have been dropped
[解析]本题应选B。本题的前一句说明一个结果，后一句则表示一个原因。
I _______have been more than six years old when the accident happened.
A. shouldn't B. couldn't C. mustn't D. needn't
[解析]从题意上分析，本题的前一句陈述一个理由，后一句则是由前一句得出的结论。故本题选[b] 。
（4）may／might have＋过去分词
表示对过去情况的一种不太有把握的可能性推测，表示“过去可能／大概已做了某事”；否定句表示“过去可能还没有做某事”。
We have proved great adventurers, but we have done the greatest march ever made in the past ten years.
A. needn’t B. may not C. shouldn’t D. mustn’t Key
（5）can／could have＋过去分词
表示“过去本来可以做某事，但实际上没有做”；否定句表示“不可能已做了某事”；疑问句表示“可能／也许已做了某事吗？”。
--- I stayed at a hotel while in New York .
--- Oh, did you? You ＿＿＿＿ with Barbara．
A. could have stayed B. could stay
C. would stay D. must have stayed
If you want to ask me why we should(1) _________English, my answer will be simple and clear. Now let me tell you the reasons one by one in the following.
In the first place, English (2)___________ an international language. If you know English, you (3)__________a trip round the world without being misunderstood.
In the second place, most valuable books, newspapers and magazines(4)_________in English. If you hope to get knowledge, you must learn English.
In the third place, English is the bridge to the outside world. If you want to go abroad for further study in the fields of medicine or technology, you will find it very important for you (5)__________your dreams.
答案
1-5.study .has become will take are written to achieve
