5. should
1) 表义务。意为"应该"（某件事宜于做），用于各种人称。例如：
① You should be polite to your teachers. 你对老师应该有礼貌。
② You shouldn't waste any time. 你不应该浪费时间。
2) 表推测，意为"想必一定、照说应该、估计"等。例如：
① The film should be very good as it is starring first-class actors. 这部新电影是一流演员主演的，估计拍得很好。
② They should be home by now. 照说他们现在应当已经到家了。
3)（表示不确定）万一。例如：
① If I should see him, I'll tell him. 万一我见到他，我就告诉他。
② If it should rain tomorrow, the sports meeting would be postponed. 万一明天下雨,比赛就延期举行。"
6. would
1) 表意愿。例如：:
① They would not let him in because he was poorly dressed. 他们不让他进去因为他衣着破旧。
② I said I would do anything for you. 我说过我愿意为你做任何事。
2) 表委婉地提出请求、建议或看法。例如：
① Would you mind cleaning the window? 请把窗户擦一下好吗？
② They wouldn't have anything against it. 他们不会有什么反对意见。
3) 表过去反复发生的动作或过去的一种倾向。例如：:
Every time she was in trouble, she would go to him for help. 她每遇到麻烦都会向她求助。他告诉我盒子打不开了。
7.ought to
1) 表义务，意为"应该"（因责任、义务等该做），口气比should稍重。例如：
① You are his father. You ought to take care of him.你是他父亲，应当管他。
② You oughtn't to smoke so much. 你不应该抽这么多烟。
2) 表推测，暗含很大的可能，语气较弱。例如：
① Han Mei ought to know his telephone number. 韩梅该知道他的电话号码。
② There's a fine sunset; it ought to be a fine day tomorrow. 今天有晚霞，明天应该是个好天。
8. used to
表示过去的习惯动作或状态，现在不复发生或存在。疑问式和否定式有两种。例如：i
① There used to be a building at the street corner, but it has been pulled down. 街道拐角处过去有座楼房，现在拆了。
② I usedn't (didn't use) to smoke. 我过去不抽烟。j }F
③ Used you (Did you use) to go to school on foot? 你过去常步行去学校吗？
9.特殊情态动词need和dare的用法：
need和dare既可用作情态动词，也可用作实义动词。用作情态动词时，主要用于否定句和疑问句。用作实义动词时，可用于各种句式。
1) 用作情态动词。例如：|
① You needn't telephone him now. 你现在不必打电话给他。
② I don't think you need worry. 我想你不必发愁。
③ She dare not go out alone at night. 她晚上不敢一个人出去。
④ How dare you say I'm unfair? 你竟敢说我不公平？_
2) 用作实义动词。例如：
① You don't need to do it yourself. 你不必亲自做这件事。
② We need to tell them the news. 我们需要把这消息告诉他们。
③ The table needs painting (to be painted.). 桌子需要油漆一下。
④ We should dare to give our own opinion. 我们要敢于提出自己的观点。
⑤ He did not dare (to) look up. 他不敢抬头看。
⑥ I dare say he'll come again. 我想他会再来的。
【注意】（I dare say…为固定习语）
◆ 难点突破
1. 情态动词后跟完成式和进行式的用法
1) 情态动词+动词完成式
情态动词+动词完成式即"情态动词+ have + done分词"，表示对过去行为或动作进行推测、评论或判断。
must have done 表示对过去某事的肯定猜测。其否定或疑问形式都用can(could) 来表示。 例如：
① Since the road is wet, it must have rained last night.
② He can't have missed the way. I drew him a map.
③ The dictionary has disappeared. Who could have taken it?
当然对现在发生或将来发生的事情,要用must do 表示猜测, 否定为can't do。例如：
④ He must understand that we mean business.
⑤ You must be hungry after a long walk.
may / might have done表示推测过去某事"也许"发生了.may 比 might 表示的可能性在说话人看来稍大些。例如：
⑥ I can't find my keys. I may / might have left them at the school yesterday.
could have done 在肯定句型中, 往往用作委婉的批评. 本应该做什么,而没做; 有时也用作猜测。例如：
⑦ You could have told us earlier.
⑧ Tom could have taken the dictionary.
ought to / should have done和 ought not to / shouldn't have done用于对已发生的情况表示"责备"、"不满"，分别表示"本应该…"和"本不应该…"。例如：
⑨ With all the work finished, I should have gone to the party last night.
⑩ You ought not to have made fun of him. He is not the one you laugh at but learn from.
needn't have done 表示过去做了某事，但没有做的必要， 意为"本没必要…"。例如：
⑾ You needn't have waken me up; I don't have to go to work today.
【注意】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：
⑿ ---I wonder how Tom knew about your past.
---He must / could / may / might have heard of it from Mary.
2) 情态动词+动词进行式
情态动词+行为动词进行式（即情态动词+ be + doing形式），表示推测或评论某动作现在是否正在进行。例如：
① He must be playing basketball in the room.
② She may be staying at home.
3) 情态动词+动词完成进行式
情态动词+行为动词完成进行式（即情态动词+ have been + v-ing形式），表示推测或评论过去某动作是否正在进行或一直在进行。例如：
① They should have been meeting to discuss the problem.
② He may / might have been buying stamps in the post office when you saw him.|
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