【正文】 ago. 他可能在家嗎？不，他不可能在家，因為我5分鐘之前才在街上遇到他。 may (might) 1）表示請求、可以、允許。 You may drive the tractor. 你可以開那臺拖拉機。 2)表建議（可和as well 連用） You may（might）as well stay where you are. 你還是原地待著好。（may as well 有“還是……的好”的含義）3）表可能（事實上）。可以指過去時間，也可以指現(xiàn)在時間，但語氣更加不肯定，只能用于肯定句和否定句。 He may be at home. 他可能在家。 She may not know about it. 她可能不知道這件事。 He was afraid they might not agree with him. 他擔(dān)心他們可能不同意他的意見。 They might be having a meeting, but I’m not sure. 他們有可能在開會，不過我不肯定。 must 1）表示必須、必要 We must do everything step by step .我們必須按部就班地做一切事情。 2)must 的否定式有兩個：當(dāng)回答由must引起的問題時，否定答復(fù)要用needn’t或don’t have to 表示“不必”、“無須”、“用不著”、“ 3）表示推測語氣的用法，意為“準(zhǔn)是、一定”等，只用于肯定句，并且要有充足的理由說明。 He must have passed the exam, because he looked so happy. 他一定通過考試了，因為他看起來如此的開心。 4. have to have to的含義與must是很接近的,只是have to 比較強調(diào)客觀需要，must著重說明主觀看法。 I must clean the room.（主觀想法）I have to clean the room.（客觀需要） 另外，have to 能用于更多時態(tài)： We had to be there at ten .我們得在十點鐘到那里。 We will have to reconsider the whole thing. 這一切我們將不得不重新加以考慮。 have to 的否定式：don’t have to do 表示“不必做……”之意。 would. 1）表意愿。 They would not let him in because he was poorly dressed. 他們不讓他進去因為他衣著破舊。 I said I would do anything for you. 我說過我愿意為你做任何事。 2）表過去反復(fù)發(fā)生的動作或過去的一種傾向。 Every time she was in trouble, she would go to him for help. 她每遇到麻煩都會向她求助。他告訴我盒子打不開了。 ought to . 表義務(wù)，意為“應(yīng)該”（因責(zé)任、義務(wù)等該做），口氣比should稍重。 You are his father. You ought to take care of him. 你是他父親，應(yīng)當(dāng)管他。 You oughtn’t to smoke so much. 你不應(yīng)該抽這么多煙。 used to . 表示過去的習(xí)慣動作或狀態(tài)，現(xiàn)在不復(fù)發(fā)生或存在。疑問式和否定式有兩種。 He used to live in the countryside, but now he lives in the ，現(xiàn)在住在城里。 There used to be a building at the street corner, but it has been pulled down. 街道拐角處過去有座樓房，現(xiàn)在拆了。 I usedn’t (didn’t use) to smoke. 我過去不抽煙。 Used you (Did you use) to go to school on foot? 你過去常步行去學(xué)校嗎？ 難點釋疑：（一）need和dare的用法比較 need和dare既可用作情態(tài)動詞，也可用作實義動詞。用作情態(tài)動詞時，主要用于否定句和疑問句。用作實義動詞時，可用于各種句式。 You needn’t telephone him now. 你現(xiàn)在不必打電話給他。 I don’t think you need worry. 我想你不必發(fā)愁。 She dare not go out alone at night. 她晚上不敢一個人出去。 Not one of them dared mention this. 他們誰也不敢提這件事。 You don’t need to do it yourself. 你不必親自做這件事。 We need to tell them the news. 我們需要把這消息告訴他們。 The table needs painting (to be painted.). 桌子需要油漆一下。 We should dare to give our own opinion. 我們要敢于提出自己的觀點。 He did not dare (to) look up. 他不敢抬頭看。 （二）情態(tài)動詞后跟完成式和進行時的用法 ，表“應(yīng)當(dāng)已經(jīng)……”，“想必已經(jīng)……”，“本來可以……”等意。 I should have finished the work earlier. 我應(yīng)當(dāng)早一點完成這項工作的。 He isn’t here. He must have missed the train. 他還未到，一定是沒趕上火車。 Where can (could) he have gone? 他能到那里去了呢？ You may (might) have read about it. 你可能在報上已經(jīng)讀到這件事了。 You could (might) have been more careful. 你本來可以更細心的。 He needn’t have worried about it. 他本不必為此事?lián)摹?There was a lot of fun at yesterday’s party. You ought to have e, but why didn’t you? 昨天的聚會非常有意思。你本應(yīng)該來，為何不來呢？ 2. 情態(tài)動詞后跟進行時，表示“想必正在……”，“可能正在……”，“應(yīng)當(dāng)正在”等意。 It’s twelve o’clock. They must be having lunch. 現(xiàn)在是十二點。他們一定正在吃飯。 They may be discussing this problem now 他們可能正在論討這個問題。 六、不定式1. 不定式的構(gòu)成 1) 不定式的一般式. 不定式的一般式所表示的動作通常與主要謂語的動作同時或幾乎同時發(fā)生，或是在它之后發(fā)生。如： They invited us to go there this summer. 他們邀請我們今年夏天去那兒。 He stood aside for me to pass. 他站到一邊讓我通過。 2) 不定式的完成式 . 不定式的完成式所表示的動作在謂語所表示的動作之前發(fā)生，它在句中可作表語、狀語、賓語，有時也可作主語、定語等。如： She seemed to have heard about this matter. 她似乎已聽說過這件事。 I am sorry to have kept you waiting so long. 我很抱歉讓你等了這么久。 I meant to have told you about it, but I happened to have an important thing to do. 我本來想告訴你這件事的，但我碰巧有一件重要的事要做。It has been an honor for me to have traveled so much in your country. 對我來說，在你們國家旅行這么多地方是一件很榮幸的事情。 3) 不定式的進行時 . 不定式的進行時表示正在進行的與謂語動詞同時發(fā)生的動作。它在句中可以用作除謂語以外的所有成分。如： He pretended to be listening to the teacher carefully. 他假裝在認(rèn)真地聽老師講課。 4) 動詞不定式的否定形式是由not或never加不定式構(gòu)成。 Try not to be late again next time. 盡量下次不要再遲到。 He wished us never to meet her again. 他希望我們永遠不要再見到她。 5) 疑問詞+動詞不定式： 不定式和疑問詞whether, what, which, whom, where, when, how, why等連用可以在句中起名詞的作用，通常跟在tell, know, show, decide, learn, wonder, explain, advise, teach, discuss, find out等動詞后面作賓語，有時也可以充當(dāng)主語、表語等。如： On hearing the news, he didn’t know whether to laugh or to cry. 聽到這個消息，他不知道該哭還是該笑。 When to hold the meeting has not decided. 什么時候開會還沒有決定。 The most important problem is how to get so much money. 最重要的事情是如何搞到這么多錢。 介詞后一般不直接接不定式，但可以接疑問詞+不定式短語作賓語。如： Mary gave some advice on how to learn English. 瑪麗提了一些如何學(xué)習(xí)英語的建議。 I have no idea of how to do it. 我不知道該怎么做。 2. 不定式的語法作用 . 1) 不定式作主語： To see once is better than to hear a hundred times. 百聞不如一見。 To master a foreign language is not an easy thing. 掌握一門外語不是一件容易的事。 在很多情況下，人們通常用it作為形式上的主語，而把不定式短語移到謂語之后，使句子顯得平穩(wěn)一些。如： It’s good manners to wait in line. 排隊等候是很有禮貌的。 It made us very angry to hear him speak to his mother like that. 聽到他那樣跟他媽媽說話我們很生氣。 2) 不定式作表語： The most important thing is to put theory into practice. 最重要的事情是把理論付諸實踐。 The greatest happiness is to work for the happiness of all. 最大的幸福就是為大家的幸福而工作。 I feel it a great honor to be invited to speak at the meeting before so many students. 我覺得被邀請在會上面對這么多學(xué)生發(fā)言是一件很光榮的事情。 4) 不定式作補語：. ①不定式可以和名詞或代詞一起構(gòu)成復(fù)合結(jié)構(gòu)作動詞的賓語，這時不定式被稱為賓語補足語。如： I would like you to help me with my English exercises. 我想請你幫我做英語練習(xí)。I never expected the shoes to be worn out so soon. 我從來沒想到鞋這么快就穿破了。注意：動詞help后面接不定式作賓語或賓語補足語可以帶to也可以不帶to。如： Who can help me (to) carry this heavy box? 誰能幫我拎這個重箱子？ ②在make, let, have等使役動詞和see, watch, notice, hear, feel等感官動詞后的復(fù)合賓語中，動詞不定式不帶to。 I often hear her sing in the next room. 我經(jīng)常聽到她在隔壁唱歌。 They make the baby go to bed at 7:00 . every day. 他們每天讓孩子晚上7：00上床睡覺。 注意：當(dāng)使役動詞和感官動詞變?yōu)楸粍诱Z態(tài)時，不定式就成了主語補語，作主語補語的不定式必須加to。如： Though he had often made his little sister cry, today he was made to cry by his little sister. 盡管他經(jīng)常弄哭他的小妹妹，但今天他卻被他的小妹妹弄哭了。 He is often heard to sing the song. 經(jīng)常有人聽到他唱這首歌。 ③以be said, be reported, be known, seem, happen, prove, appear等構(gòu)成謂語的句子中，動詞不定式通常也可看作主語補語。如： More than 20 people were reported to have been killed in the accident. 據(jù)報道，有20多個人死于事故。 I happened to be talking with him when he was hit by a car. 他被汽車撞的時候，我碰巧在和他談話。