情态动词用法

1、、在虚拟语气中的用法1. should have done过去本应该做某事却未做shouldnt have done2. ought to have doneoughtnt to have done3. need have doneneednt have done、表推测的用法过去本不该做某事却做了过去本应该做某事却未做过去本不该做某事却做了过去本有必要做某事却未做过去本没必要做某事却做了4. could （ 不能用 can） have done过去本能够做某事却未做 注意：其否定形式 couldnt have done 没有虚拟语气的用法， couldnt have done 只能表推测，相

2、当于 cant have done ，意为： “过去不可能做了某事。”5. might （ 不能用 may） have done 过去本可以做某事却未做 注意：其否定形式 might not have done 没有虚拟语气的用法， might not have done 只能表推测 ，相当于 may not have done，意为：“ 过 去可能没有做某事 。”1. must have done表示对过去某事的肯定猜测，译为： 过去肯定做了某事 。不存在 mustnt have done 的形式。其否定或疑问形式须用 can（could） 来 表示 . 例如：Since the road

3、is wet, it must have rained last night.既然路是湿的，那昨天晚上肯定下雨了。He cant have missed the way. I drew him a map.他不可能迷路。我（当时）给他画了张图。“The dictionary has disappeared. Whoc ould have taken it ” 词 典不见了，（过去）谁可能把它拿走了2. may / might have donemay / might have done 表示“过去可能做了某事 ”。may 比 might 表示的可能性在说话人看来稍大些 。 may/might

4、not have done 表示 “过去可能没有做某事 。”例如：I cant find my keys. I may / might have left them at the school yesterday. 我找不到我的钥匙了。我可能昨天把他们落在学校了。 John may/might not have passed the exam; he looks very sad. 约翰可能没有通过考试。他看起来很忧伤。注意： may/might have done 表推测不能用于疑问句中。3. can/could have done 表推测一般用在否定句和疑问句中，表示 不相信或怀疑的态度。

5、Can/Could he have passed the exam 他可能通过了考试吗I think that he couldn t/cant have gone abroad. I saw him just now.我认为他不可能出国了。我刚才还看见他了。 注：表示推测过去某动作发生的可能性时， 就表示的可能性程度而言， must 最大， could 其次， may 更次之， might 最小。例如： 英语里形容词的比较级有三个等级 , 原级( positive degree )as+原级+as.如： Im as tall as my twin brother.我和我的双胞胎哥哥一样高 .

6、比较级 (comparative degree)比较级+than. 如：My father is younger than my uncle.我的父亲比我的伯父年轻 .最高级 (superlative degree )The+ 最高级1. Sorry Im late. I have turned off the alarm clockand gone back to sleep again.( 2000 北京春季)A. mightB. shouldC. canD.will答案为 A 。表推测的用法。句意：对不起，我迟到了。我(当时)兴 许是关了闹钟又回去睡觉了。 might 相当于 may,

7、但语气更加不肯2. I was really anxious about you. You home withouta word. （ 01 全国）A. mustnt leave B. shouldnt have left C. couldnt have leftD. neednt leave答案为 B 。虚拟语气用法。句意：我（那时）真地很担心你。你本不 应该不留个话就离开家。3. I ll tell Mary about her new job tomorrow. You her last week.（ 04 福建）Aought to tell Bwould have told Cmust

8、 tell D should have told答案为 D。虚拟语气用法。句意： - 我明天要告诉她我的新工作的 情况。 - 你本应该上周告诉她。4. Tom graduated from college at a very young age. Oh, he have been a very smart boy then.（ 04 全国IV）A. could B. should C. might D. must答案为 D。表推测的用法。句意： 汤姆 很年轻的时候就大学毕业 了。哦，他肯定是一个很聪明的男孩儿。5. He have completed his work; otherwise,

9、he wouldnt北京卷）be enjoying himself by the seaside. （05A. should B. must C. wouldnt D. cant答案为 B。用法同 4 题。句意：他肯定做完了工作，不然他就不会在 海边痛快地玩儿了。6. Do you know where David is I couldnt find him anywhere. Well. He have gone far his coats still here.（ 05湖北卷）A shouldnt B mustnt C cant D wouldnt答案为 C。表推测的用法。句意：你知道大卫

10、在哪儿吗我哪儿也找 不到他。瞧， 他不可能走远他的上衣还在这儿呢。 cant 相当与 couldnt ，但后者语气更加委婉。四、练习1. The womanb iologist stayed in Africa studying wild animals for 13 years before she returned. Oh, dear! She a lot of difficulties! （05江苏卷 ）A. may go throughB. might go throughC. ought to have gone through D. must have gone through2.

11、 I have lost one of my gloves. I it somewhere. （05北京春季）A. must dropB. must have droppedC. must be dropping D. must have been dropped3. Mr. White at 8:30 for the meeting, but hedidnt showup. （ 04 广西）A. should have arrived B. should arriveC. should have had arrived D. should be arriving4. He paid for a seat, when he have entered free.（05山东卷）A. could B. would C. must D. need5. Tom is never late for work. Why is he absent today Something to him. （05江西卷 ）A must happenB should have happenedC could have happened D must have happened6. I have been more than six years old when the accidenthappened.