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情态动词是高中英语语法的一个重要部分，而“情态动词+have done”结构表示推测和虚拟语气是对此知识点考查的一个重难点。你是否熟知并能灵活运用它呢？
一、表示对过去的推测
1．肯定句中：
（1）must have done “一定已经”
It is wet outside. It must have rained last night.
（2）may/might/could have done “可能已经”
She looks unhappy. She may/might/could have known the news.
2．否定句中：
（1）can/could not have done “不可能已经”
He can/could not have told a lie, because he is always honest.
（2）may/might not have done “可能不，可能没有”
She may/might not have achieved her aim, but her effort is a good one.
3．疑问句中：
Can/Could +sb/sth + have done…?“可能已经…?”
Can/Could he have gone to Wuhan?
小结：1. 凡是对过去的推测，一般都用“情态动词+have done”结构。
2. 表推测时： must 只用于肯定句中（mustn’t 不能表推测，只表禁止）；can 用于否定句和疑问句中（can 一般不用于肯定句中表推测，could则可以用于肯定句、否定句和疑问句中）； may/might 用于肯定句和否定句中。
二、表对过去的虚拟假设
1. could have done“本能够”（强调本有能力做某事却没有做）
You could have helped me yesterday, but you didn’t.
2. might have done“本可能” （某事本可能会发生，却没有发生）
The knife is so sharp. It might have hurt you. (It didn’t hurt you.)
3. would have done“本想，本会”（强调一种主观意愿）
I would have invited you to go shopping yesterday, but I was afraid that you were busy. (I didn’t invite you.)
4. should/ought to have done“本该做某事却没有做”
You should have told me the news earlier. (You didn’t tell me earlier.)
5. should not/ought not to have done“本不该做某事却做了”
You should not have talked so much in class. (You talked so much.)
6. needn’t have done “本没必要做某事却做了”
You needn’t have bought such an expensive watch for her. (You bought it for her.)
小结：
could have done和might have done既可以表对过去的推测，也可以表对过去的虚拟假设；而can have done和may have done只能表对过去的推测。
三、解题思路
1. I have lost one of my gloves. I__________(一定弄掉了) it somewhere. (drop)
解题思路：1. 判断此题是情态动词表推测还是表虚拟。此题是表推测。2.判断是对过去、现在还是将来的推测。此题是对过去的推测，所以要用“情态动词+have done”结构。3. 判断是肯定句、否定句还是疑问句，从而确定所选的情态动词。此题答案为：must have dropped.
2. He paid for a seat, when he__________ (本可以进入) free. (enter)
解题思路：1. 判断此题是情态动词表推测还是虚拟。此题是表虚拟假设。2. 判断是对过去、现在还是将来的虚拟假设.此题是对过去的虚拟，所以要用“情态动词+have done”结构。3. 根据句意确定所选的情态动词。所以此题答案为：could have entered.
四、完成句子演练
1. Mr. Wang__________（应该到达）at 8:30, but he didn’t show up. (arrive)
2. Sorry, I am late. I__________（可能关掉了) the alarm clock and gone back to sleep again. (turn)
3. My sister met him at the Grand Theater yesterday afternoon, so he__________（不可能参加了）your lecture. (attend)
4. I got up early, but I__________（不必这么做）, because it was Sunday. (do)
5. Why didn’t you tell me about your problem? I__________（本来能够帮助）you. (help)
6. You __________（不该离开） without saying a word. You don’t know how anxious we were about you. (leave)
7. I didn’t hear the phone. I__________（一定是入睡了）.(fall)
8. You should not have swum in that river. You __________（本来可能溺水）. (drown)
9. He__________（不可能在看） TV at 8 last night. He has gone to New York. (watch)
10. He__________(可能没有尽力） his best to do it. In fact, he could do it better. (try)
参考答案：
1. should have arrived (虚）
2. may/might/could have turned off （推）
3. can’t/couldn’t have attended （推）
4. needn’t have done so （虚）
5. could have helped （虚)
6. shouldn’t have left (虚）
7. must have fallen asleep （推）
8. might have drowned （虚）
9. can’t /couldn’t have been watching （推）
10. may/might not have tried (推）
一、表示对过去的推测
1．肯定句中：
（1）must have done “一定已经”
It is wet outside. It must have rained last night.
（2）may/might/could have done “可能已经”
She looks unhappy. She may/might/could have known the news.
2．否定句中：
（1）can/could not have done “不可能已经”
He can/could not have told a lie, because he is always honest.
（2）may/might not have done “可能不，可能没有”
She may/might not have achieved her aim, but her effort is a good one.
3．疑问句中：
Can/Could +sb/sth + have done…?“可能已经…?”
Can/Could he have gone to Wuhan?
小结：1. 凡是对过去的推测，一般都用“情态动词+have done”结构。
2. 表推测时： must 只用于肯定句中（mustn’t 不能表推测，只表禁止）；can 用于否定句和疑问句中（can 一般不用于肯定句中表推测，could则可以用于肯定句、否定句和疑问句中）； may/might 用于肯定句和否定句中。
二、表对过去的虚拟假设
1. could have done“本能够”（强调本有能力做某事却没有做）
You could have helped me yesterday, but you didn’t.
2. might have done“本可能” （某事本可能会发生，却没有发生）
The knife is so sharp. It might have hurt you. (It didn’t hurt you.)
3. would have done“本想，本会”（强调一种主观意愿）
I would have invited you to go shopping yesterday, but I was afraid that you were busy. (I didn’t invite you.)
4. should/ought to have done“本该做某事却没有做”
You should have told me the news earlier. (You didn’t tell me earlier.)
5. should not/ought not to have done“本不该做某事却做了”
You should not have talked so much in class. (You talked so much.)
6. needn’t have done “本没必要做某事却做了”
You needn’t have bought such an expensive watch for her. (You bought it for her.)
小结：
could have done和might have done既可以表对过去的推测，也可以表对过去的虚拟假设；而can have done和may have done只能表对过去的推测。
三、解题思路
1. I have lost one of my gloves. I__________(一定弄掉了) it somewhere. (drop)
解题思路：1. 判断此题是情态动词表推测还是表虚拟。此题是表推测。2.判断是对过去、现在还是将来的推测。此题是对过去的推测，所以要用“情态动词+have done”结构。3. 判断是肯定句、否定句还是疑问句，从而确定所选的情态动词。此题答案为：must have dropped.
2. He paid for a seat, when he__________ (本可以进入) free. (enter)
解题思路：1. 判断此题是情态动词表推测还是虚拟。此题是表虚拟假设。2. 判断是对过去、现在还是将来的虚拟假设.此题是对过去的虚拟，所以要用“情态动词+have done”结构。3. 根据句意确定所选的情态动词。所以此题答案为：could have entered.
四、完成句子演练
1. Mr. Wang__________（应该到达）at 8:30, but he didn’t show up. (arrive)
2. Sorry, I am late. I__________（可能关掉了) the alarm clock and gone back to sleep again. (turn)
3. My sister met him at the Grand Theater yesterday afternoon, so he__________（不可能参加了）your lecture. (attend)
4. I got up early, but I__________（不必这么做）, because it was Sunday. (do)
5. Why didn’t you tell me about your problem? I__________（本来能够帮助）you. (help)
6. You __________（不该离开） without saying a word. You don’t know how anxious we were about you. (leave)
7. I didn’t hear the phone. I__________（一定是入睡了）.(fall)
8. You should not have swum in that river. You __________（本来可能溺水）. (drown)
9. He__________（不可能在看） TV at 8 last night. He has gone to New York. (watch)
10. He__________(可能没有尽力） his best to do it. In fact, he could do it better. (try)
参考答案：
1. should have arrived (虚）
2. may/might/could have turned off （推）
3. can’t/couldn’t have attended （推）
4. needn’t have done so （虚）
5. could have helped （虚)
6. shouldn’t have left (虚）
7. must have fallen asleep （推）
8. might have drowned （虚）
9. can’t /couldn’t have been watching （推）
10. may/might not have tried (推）