ought to的用法1. Ought to表示应该。如：

　　You ought to take care of him.

　　2. 表示推测。注意与must表示推测时的区别：

　　He must be at home by now. （断定他已到家）

　　He ought to be home by now. （不十分肯定）

　　This is where the oil must be. （比较直率）

　　This is where the oil ought to be. （比较含蓄）

　　3. “ought to + have + 过去分词”表示过去应做某事而实际未做。如：

　　You ought to have asked him (but you didn't).

　　这时，ought to和should可以互相换用。

　　注意：在美国英语中，ought to用于否定句和疑问句时，to可以省略。如：

　　Ought you smoke so much?

　　You oughtn't smoke so much.

　　ought和should的区别：

　　1.ought语气略强。

　　2.should较常用。

　　3.ought在美国英语中用的很少，而should却相当常用。

　　4.ought属正式用语。

　　注：由于ought to 没有过去式，所以在直接引语变间接引语的过程中，就不再变化. used to，had better，would rather的用法1. Used to表示过去的习惯动作或状态，现在已不存在，在间接引语中，其形式可不变。如：

　　He told us he used to play football when he was young.

　　在疑问句、否定句、否定疑问句或强调句中，可有两种形式：

　　疑问句

　　Did you use to go to the same school as your brother?

　　Used you to go to the same school as your brother?

　　否定句

　　I usedn't to go there.

　　I didn't use to go there.

　　Usedn't 亦可拼作usen't，但发音皆为['ju:snt]。

　　否定疑问句

　　Usen't you to be interested in the theatre?

　　Didn't you use to be interested in the theatre?

　　强调句

　　I certainly used to smoke, but it was a long time ago.

　　I certainly did use to smoke, but it was a long time ago.

　　其反意疑问句或简略回答中，也有两种形式：

　　She used to be very fat, didn't she? （口语+常用）/ use(d)n't she? （正式+过时）

　　Did you use to play chess? Yes, I did.

　　Used you to get up early in the morning? Yes, I did. (Yes, I used to.)

　　2. Had better意为“最好”，后接不带to的不定式。如：

　　— We had better go now.

　　— Yes, we had (we'd better / we had better).

　　Hadn't we better stop now? (Had we better not stop now?)

　　I think I'd better be going. （用于进行时态，表“最好立即”）

　　You had better have done that. （用于完成时态，表未完成动作）

　　注：①had best与had better同意，但较少用。②You had better … 用于同辈或小辈，对长辈不可用。

　　3. Would rather意为“宁愿”，表选择，后接不带to的不定式。如：

　　I'd rather not say anything.

　　Would you rather work on a farm?

　　— Wouldn't you rather stay here?

　　— No, I would not. I'd rather go there.

　　由于would rather表选择，因而后可接than。如：

　　I would rather work on a farm than in a factory.

　　I would rather watch TV than go to see the film.

　　I would rather lose a dozen cherry trees than that you should tell me one lie.

　　I'd rather you didn't talk about this to anyone. （句中的'd rather不是情态动词，would在此是表愿望的实义动词）

　　注：由于used to，had better同ought to一样没有过去式，所以在直接引语变间接引语的过程中，也不再变化.

　　1. — What does the sign over there read?

　　—“No person __________ smoke or carry a lighted cigarette，cigar or pipe in this area.” (2007四川卷)

　　A. will                             B. may

　　C. shall                            D. must

　　本帖隐藏的内容

　　答案：C  句子说那边的表语说什么？谁也不能在这里抽烟。。。shall在陈述句中用于第二人称和第三人称时，可表示说话者的允诺、告诫、威胁、命令、规定、必然性等，如：You shall suffer for this. 你会为此事吃苦头的。(表威胁) Tell him that he shall have the book tomorrow. 告诉他这本书明天给他。(表允诺) Persons under 18 shall not be employed in night work．不满18岁的人不得雇佣干夜间工作。(表规定)

　　2. —What do you think we can do for our aged parents?

　　—You __________ do anything except to be with them and be yourself. (2007重庆卷)

　　A. don’t have to                 B. oughtn’t to

　　C. mustn’t                        D. can’t

　　本帖隐藏的内容

　　答案：A 句子说我们可以为父母做些什么呢？你不必做什么，只要陪着他们，做个好孩子就行了，don’t have to意为“不必”。句意是：你不必做什么，只需陪陪他们，真诚地对待他们。