Unit1-Unit2 情态动词学案 2022-2023学年高中英语外研版必修第二册

必修二 M1-2 情态动词 情态动词表示说话者对某一行为的态度和观点，主要包括揣测、判断、需要、可能、意愿等。①情态动词不能独立作谓语，只能和动词原形一起构成谓语。②没有人称和数的变化（have to例外，用于第三人称单数时用has to）。③每个情态动词都有多个意义。④情态动词有助动词的作用，可用来构成否定句疑问句及用于简明答语。⑤个别情态动词（can，may，shall，will)有现在式和过去式两种形式，过去式用来表达委婉的语气，时态性不强，可用于过去、现在或将来。⑥情态动词属不及物动词，故没有被动语态。英语中常用的情态动词主要有can, could, may, might, must, have to, will, would, shall, should, need, had better… 一.情态动词be able to, have to, had better, dare, need的用法（M1） 1. be able to表示“经过努力而成功地做成某事”，有人称和时态的变化，不能与can连用。 e.g. It took me a long time before I was able to fully appreciate what they had done for me. 理解 If we keep trying, we will be able to achieve our goals. 2.have to表示“不得不,必须”，强调客观上的必要性，有人称和时态的变化。否定式为don’t/doesn't/didn't have to,“不必”。 e.g. You have to wear uniform when on duty, don't you? If you earn more than £ 5,000, you will have to pay tax. We don't have to rush —there's plenty of time. 3. had better表示"应该,最好"，没有人称和时态的变化。否定式had better not。 e.g. We'd better leave now or we'll miss the bus. You'd better not tell Oliver the news. 4.1 dare作情态动词常用于疑问句、否定句及条件句中，表示“敢于,胆敢”，没有人称变化，但有过去式。 e.g. He daren't speak English in public. They hardly dared breathe as somebody walked past the door! 4.2 dare也可作实义动词，其用法如下： ①作实义动词时，有人称、时态和数的变化；②在肯定句中，常用dare to do sth； ③在否定和疑问句中，可接带to或不带to的不定式； ④构成否定句和疑问句时，要借助do，does，did等助动词。 e.g. He dares to challenge all kinds of difficulties. He doesn't dare (to) go there alone. 5.1 need作情态动词多用在疑问句和否定句中，表示“需要”,没有时态和人称的变化。对need引出的一般疑问句,作肯定回答时要用must，作否定回答时要用needn't 或don't have to。 e.g. If she wants anything, she need only ask. This is free service; you needn't pay for it. -Need I hand in the application now? -Yes, you must. - No, you don't have to. 5.2 need也可作实义动词，有时态、人称和数的变化，后加n./ pron./ to do/ doing… 构成否定式和一般疑问句时要借助do/does/did。 ①sb need (sb./ sth.) to do sth，否定形式：don’t need to do sth. e.g. -Does he need to tell you the truth? – Yes, he does./ No, he doesn’t. ②need 的被动含义：sth need doing = sth need to be done,表示“(某事物)需要…”，用主动形式表示被动含义，类似的有：sth need/ want/ require doing e.g. The flow