2019届英语高考二轮复习语法专题 专题7 情态动词及虚拟语气

专题7　情态动词和虚拟语气 考纲展示　命题探究 基础点 1　can和could的用法 (1)表示“能力”，can表示现在的能力，could表示过去的能力。 Can you lift this heavy box? 典例1　　—No one________be compared with Yao Ming in playing basketball. —Oh, you are really his big fan. (2)表示推测，意为“可能”，常用于否定句和疑问句。can比could语气强。 He can't be our manager. He has gone to Beijing. 典例2　　—How's your new babysitter? —We ________ask for a better one. All our kids love her so much. (3)表示“请求”和“许可”(could用来表示“请求”时，是委婉的说法，回答时一般用can) —Could you please do me a favor? —Yes, I can. (4)表示理论上的可能性或一时的情况，意为“有时会”，用于肯定句。 It can be very cold in April. 典例3　　—Why, my new computer is rubbish! Five hours has passed and it still hasn't finished the downloading. —Don't worry. You know, sometimes the Internet________be very slow. (5)固定结构 cannot/couldn't... too/enough无论……也不过分；越……越好 cannot/couldn't but do sth.不得不，只好 can't/couldn't help doing sth.禁不住做某事 2　may 和might的用法 (1)表示请求和许可(在疑问句中表示请求时可用might代替may，表示语气委婉，不表示过去)。 May I watch TV after supper? 特别提醒 May... do...？的否定回答用mustn't/can't。 —May I come in? —No, you mustn't/can't. 典例4　　—________I take the book out? —I'm afraid not. (2)表示可能性，意为“或许，可能”，用来表示一件事或许会发生，或是某种情况可能会存在。通常用于肯定句和否定句中，而不用于疑问句中。might比may语气更弱。 He may/might come tonight. 典例5　　—You needn't take an umbrella. It isn't going to rain. —Well, I don't know. It________do. (3)用于祈使句中表示祝愿，常用结构 May＋主语＋do! May you succeed! 典例6　　—Have you heard of the news that Britain's former Prime Minister, Baroness Thatcher, died on April 18? —Yes.________she rest in peace. (4)固定结构 may/might as well 不妨，还是……为好 may/might well＋动词原形　很可能(相当于probably) You may_as_well_tell him the truth. He may_well_stay in Beijing now. 3　must和have to的用法 (1)must意为“必须”，多指现在或将来的情况，语气强烈；have to 意为“不得不”，意义与must相近，但must表示说话人的主观看法，其否定形式为mustn't, 意为“不许，禁止”；have to则强调客观需要。 —Must I finish the homework before nine? —Yes, you must. I have_to go now, because my mother is in hospital. 特别提醒 (1)回答带有must的问句时，否定回答常用needn't或don't have to，意为“不必”。 —Must I come back before ten? —No, you needn't/don't_have_to. (2)must只有一种形式，而have to有人称、