3）表"硬要，偏要"

　　①My son must do the opposite to what we ordered.

　　②Why must you always leave your dirty clothes in the bathroom.

shall

1) 表征询意见，用于第一、第三人称疑问句。①Shall I get you some tea? ②Shall the boy wait outside?

2)表"命令、允诺、警告、决心、按规章制度、预言"等意思，用于第二、第三人称陈述句。

　　① You shall do as I say.(命令)

① You shall have my answer tomorrow.（允诺）

② He shall be sorry for it one day, I tell you. （警告）

③ Nothing shall stop us from carrying out the plan.（决心）

④ Each competitor shall wear a number.(规章)

⑥All shall die.（预言）

Should

1) 表义务，责任。意为"应该"。

　　①You should be polite to the old.

　　②You shouldn't waste any time.

1) 表推测，意为"想必一定、照说应该、估计"等。

① The film should be very good as it is starring first-class actors.

② They should be home by now.

3)表示说话人对某事不能理解，感到意外、惊异等,"竟然, 怎么会"

　　①I wonder that a person like him should make such a mistake.

　　②Why should you be so late today?

4) should用于第一人称时可以表示说话人的一种谦逊、客气、委婉的语气

①I should think it would be better to try it again. 我倒是认为最好再试一试。

②You are mistaken, I should say.依我看,你是搞错了

③I should advise you not to do that.我倒是劝你别这样做。

5) should have done // shouldn't have done本应该做而没有做//本不应该做而做了

　　①You should have done it today, for it is urgent

　　②I was really anxious about you. You shouldn't have gone home without a word. ◆竟然做过了某事 You should have been fooled by such a simple trick.

ought to 表义务，意为"应该"（因责任、义务等该做），口气比should稍重。

　　①You are his father. You ought to take care of him.

②You oughtn't to smoke so much.