情態(tài)動詞用法

1、、在虛擬語氣中的用法1. should have done過去本應(yīng)該做某事卻未做shouldnt have done2. ought to have doneoughtnt to have done3. need have doneneednt have done、表推測的用法過去本不該做某事卻做了過去本應(yīng)該做某事卻未做過去本不該做某事卻做了過去本有必要做某事卻未做過去本沒必要做某事卻做了4. could （ 不能用 can） have done過去本能夠做某事卻未做 注意：其否定形式 couldnt have done 沒有虛擬語氣的用法， couldnt have done 只能表推測，相

2、當(dāng)于 cant have done ，意為： “過去不可能做了某事。”5. might （ 不能用 may） have done 過去本可以做某事卻未做 注意：其否定形式 might not have done 沒有虛擬語氣的用法， might not have done 只能表推測 ，相當(dāng)于 may not have done，意為：“ 過 去可能沒有做某事 ?！?. must have done表示對過去某事的肯定猜測，譯為： 過去肯定做了某事 。不存在 mustnt have done 的形式。其否定或疑問形式須用 can（could） 來 表示 . 例如：Since the road

3、is wet, it must have rained last night.既然路是濕的，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（當(dāng)時）給他畫了張圖。“The dictionary has disappeared. Whoc ould have taken it ” 詞 典不見了，（過去）誰可能把它拿走了2. may / might have donemay / might have done 表示“過去可能做了某事 ”。may 比 might 表示的可能性在說話人看來稍大些 。 may/might

4、not have done 表示 “過去可能沒有做某事 ?！崩纾篒 cant find my keys. I may / might have left them at the school yesterday. 我找不到我的鑰匙了。我可能昨天把他們落在學(xué)校了。 John may/might not have passed the exam; he looks very sad. 約翰可能沒有通過考試。他看起來很憂傷。注意： may/might have done 表推測不能用于疑問句中。3. can/could have done 表推測一般用在否定句和疑問句中，表示 不相信或懷疑的態(tài)度。

5、Can/Could he have passed the exam 他可能通過了考試嗎I think that he couldn t/cant have gone abroad. I saw him just now.我認為他不可能出國了。我剛才還看見他了。 注：表示推測過去某動作發(fā)生的可能性時， 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： 英語里形容詞的比較級有三個等級 , 原級( positive degree )as+原級+as.如： Im as tall as my twin brother.我和我的雙胞胎哥哥一樣高 .

6、比較級 (comparative degree)比較級+than. 如：My father is younger than my uncle.我的父親比我的伯父年輕 .最高級 (superlative degree )The+ 最高級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答案為 A 。表推測的用法。句意：對不起，我遲到了。我(當(dāng)時)興 許是關(guān)了鬧鐘又回去睡覺了。 might 相當(dāng)于 may,

7、但語氣更加不肯2. I was really anxious about you. You home withouta word. （ 01 全國）A. mustnt leave B. shouldnt have left C. couldnt have leftD. neednt leave答案為 B 。虛擬語氣用法。句意：我（那時）真地很擔(dān)心你。你本不 應(yīng)該不留個話就離開家。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答案為 D。虛擬語氣用法。句意： - 我明天要告訴她我的新工作的 情況。 - 你本應(yīng)該上周告訴她。4. Tom graduated from college at a very young age. Oh, he have been a very smart boy then.（ 04 全國IV）A. could B. should C. might D. must答案為 D。表推測的用法。句意： 湯姆 很年輕的時候就大學(xué)畢業(yè) 了。哦，他肯定是一個很聰明的男孩兒。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答案為 B。用法同 4 題。句意：他肯定做完了工作，不然他就不會在 海邊痛快地玩兒了。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答案為 C。表推測的用法。句意：你知道大衛(wèi)

10、在哪兒嗎我哪兒也找 不到他。瞧， 他不可能走遠他的上衣還在這兒呢。 cant 相當(dāng)與 couldnt ，但后者語氣更加委婉。四、練習(xí)1. The womanb iologist stayed in Africa studying wild animals for 13 years before she returned. Oh, dear! She a lot of difficulties! （05江蘇卷 ）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 廣西）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山東卷）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.