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用 should , ought to 或 shouldn’t , ought not to She should do her homework first . They ought to finish the work on time . they ought not to be late for school . ★★★ Notes : can 和 be able to的區(qū)別 : be able to 有 人稱數(shù)和時態(tài)的變化。 Must we stay here ? No, you need n’t . ( No, you don’t have to .) must be 表示肯定的猜測,意為“一定 ……” can’t be 表示否定的猜測,意為“ 不可能 ……” She must be a nurse . I saw her in the library just now .She can’t be here . must have done 也表示肯定的猜測,意為“ 一定做過 ……” They must have cleaned the room . It’s so clean .他們一定打掃過房間了, 它這么干凈 。 swim? ___________operate the machine last week, but we can operate it now. ’t worry. You _____ return me this book tomorrow. said if he _________ask me another question. grandma is ill. You _____ talk so loudly here . can’t play with you. I __________finish my homework first. get up early tomorrow. please open the window? Can couldn’t may could can’t must must Could 9. Nobody ___________live without air. speak Chinese ?Yes ,a little. 11. The book _________ be returned before Saturday. e in ?Yes ,please. 13. You ________give up smoking at once. It’s bad for your eyes. 14. Excuse me ._________I ask you a question? 15. __________you tell me where the station is ? 16. ______ I finish the work now ?No, you _________. You _____ do it this evening. 17. May I use your edictionary ? Sorry , you _________. I am using it now . 18. Look at the ground .It’s very wet .It _______ have rained last night. can Can must Can/May must May/Can Can/Could Must needn’t can/may can’t must 同義句改寫 : must clean your room yourself. You _________ _________ clean your room yourself. 2. She can dance beautifully. She ________ ________ ________ dance beautifully. 3. Wash your face at once. You _______ wash your face ________. 4. Tom couldn’t find his bag.