2) must have+done sth., 表示對過去時間里可能發(fā)生的事情的推測,語氣較強,具有“肯定”的意思。

　　e.g. --- Linda has gone to work, but her bicycle is still here.

　　--- She must have gone by bus.

　　3) ought to have done sth.\should have done sth.本應(yīng)該做某事,而事實上并沒有做; 否定句表示“不該做某事而做了”。

　　e.g. You ought to (should) have been more careful in this experiment.

　　He ought not to have thrown the old clothes away.(事實上已扔了。)

　　注: ought to 在語氣上比should 要強。

　　4) needn’t have done sth. 本沒必要做某事

　　e.g. I dressed very warmly for the trip, but I needn’t have done so. The weather was hot.

　　5) would like to have done sth. 本打算做某事

　　e.g. I would like to have read the article, but I was very busy then.

　　7. 情態(tài)動詞should和ought to

　　should 和ought to 都為“應(yīng)該”的意思,可用于各種人稱。

　　e.g. --- Ought he to go?

　　--- Yes. I think he ought to.

　　表示要求,命令時,語氣由 should(應(yīng)該)、(had better最好)、must(必須) 漸強。

　　8. 情態(tài)動詞had better表示“最好”

　　had better 相當(dāng)于一個助動詞,它只有一種形式,它后面要跟動詞原形。

　　had better (not) do sth.

　　e.g. It is pretty cold. You’d better put on my coat.

　　She’d better not play with the dog.

　　had better have done sth.

　　表示與事實相反的結(jié)果,意為“(過去)本來最好”。

　　e.g. You had better have come earlier.

　　9. 情態(tài)動詞would rather表示“寧愿”

　　would rather (not) do

　　would rather…than…寧愿…而不愿

　　would sooner\ had rather\ had sooner表示"寧愿"、"寧可"的意思。

　　e.g. If I have a choice, I had sooner not continue my studies at this school.

　　10. will和would

　　1) would like to do = want to 想要

　　e.g. Would you like to go with me?

　　2) Will you…? / Would you like…?

　　表示肯定含義的請求勸說時,疑問句中一般用some, 而不是any。

　　e.g. Would you like some cake?

　　3) 否定結(jié)構(gòu)中用will, 一般不用would, won’t you是一種委婉語氣。

　　e.g. Won't you sit down?

　　11. need和dare

　　這兩詞既可做實義動詞用,又可做情態(tài)動詞用。作為情態(tài)動詞,兩者都常用于疑問句,否定句和條件句。并注意回答用need 提問的句子時，肯定回答用must。

　　need 作實義動詞時后面的不定式必須帶to,而dare作實義動詞用時, 后面的to時常可以被省略。

　　1) 實義動詞: need+ n. / to do sth.

　　2) 情態(tài)動詞: need,只用原形need后加do,否定形式為need not.

　　e.g. ---- Need you go yet?

　　---- Yes, I must. / No, I needn't.

　　3) need, want, require, worth(形容詞)后面接doing也可以表示被動。

　　need doing = need to be done

　　Exercises

　　1. A left-luggage office is a place where bags ____be left for a short time, especially at a railway station.

　　A. should B. can

　　C. must D. will (B)

　　2. How ___ you say that you really understand the whole story if you have covered only part of the article?

　　A. can B. must

　　C. need D. may (A)

　　3. — The room is so dirty. ___we clean it?

　　— Of course.

　　A. Will B. Shall C. Would D. Do (B)

　　4. My English-Chinese dictionary has disappeared. Who ___ have taken it?

　　A. should B. must

　　C. could D. would (C)

　　5. — Is John coming by train?

　　— He should, but he ____ not. He likes driving his car.

　　A. must B.can

　　C. need D.may (D)

　　6. — I heard they went skiing in the mountains last winter.

　　— It ____ true because there was little snow there.

　　A. may not be B. won’t be

　　C. couldn’t be D. mustn’t be (C)

　　7. It has been announced that candidates __ remain in their seats until all the paper have been collected.

　　A. can B. will C. may D. shall (D)

　　8. — I hear you’ve got a set of valuable Australian coins. ___ I have a look?

　　—Yes, certainly.

　　A. Do B. May C. Shall D. shall (B)

　　9. Oh, I’m not feeling well in the stomach, I ___ so much fried chicken just now.

　　A. shouldn’t eat

　　B. mustn’t have eaten

　　C. shouldn’t have eaten

　　D. mustn’t eat (C)

　　10. I was really anxious about you. You ___ home without a word.

　　A. mustn’t leave

　　B. shouldn’t have left

　　C. couldn’t have left

　　D. needn’t leave (B)