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E.g: I must go to school now. I must go to school tomorrow. /I will have to go to school tomorrow. I had to go to school yesterday. Nếu không chắc chắn nên dùng từ nào thì thông thường để "an toàn" hơn ta nên dùng have - Must còn dùng để đưa ra sự suy luận dựa vào lập luận logic E.g: She must be upstairs. We've looked everywhere else. (Cô ta chắc là ở trên tầng. Chúng tôi đã tìm mọi nơi khác.) - Must + be/ feel + adj: để bày tỏ sự thấu hiểu cảm giác của ai đó E.g: You must be tired after that trip. (Bạn chắc hẳn rất mệt sau chuyến đi đó.) Mustn't và Don't have to Must not (mustn't) khác hoàn toàn với don't/ doesn't have to + Mustn't: không được làm gì đó (chỉ sự cấm đoán) E.g: You mustn't tell the truth. (Bạn không được phép nói ra sự thật) + Don't have to = Don't need to: không cần làm gì, không phải làm gì (nhưng bạn có thể làm nếu bạn muốn) E.g: You don't have to get up early. (Bạn không cần thức dậy sớm đâu.) - Must + have + PP: chắc hẳn đã, hẳn là Diễn tả sự suy đoán hay kết luận logic dựa vào thực tế ở quá khứ (to draw a conclusion about something happened in the past) E.g: Mary passed the exam with flying colors. She must have studied hard. (Mary đã thi đậu với kết quả cao. Cô ấy chắc hẳn đã học chăm chỉ.) Must + have been + Ving: chắc hẳn lúc ấy đang E.g: I didn't hear the doorbell. I must have been gardening behind the house. (Tôi đã không nghe thấy chuông cửa. Chắc hẳn lúc ấy tôi đang làm vườn phía sau nhà.) ■ BÀI TẬP VẬN DỤNG CƠ BẢN Bài 1: Choose the best option in the bracket to complete the sentences. 1. Yesterday I (must/ mustn't/ had to) finish my English project. 2. He will (must/ have to/ has to) wait in line like everyone else. 3. We (must be/ mustn't / have to) on time for work. 4. We (have to not/ must/ mustn't) forget to take the chicken out of the freezer. 5. If you are under 15, you (have/ must/ mustn't) to get your parents' permission. 6. Your child may (have to/ had to/ must) try on a few different sizes. 7. The doctor (must/ mustn't/ have to) get here as soon as he can. 8. Do you (have to/ must/ mustn't) work next weekend? 9. Bicyclists (mustn't/ must/ has to) remember to signal when they turn. 10. Susan, you (mustn't/ must/ have to) leave your clothes all over the floor like this.
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Bài 2: Choose the best answer (A, B, C or D) to complete the following sentences. 1. You__________use your mobile phone in the exam. A. oughtn't to B. mustn't C. don't have to D. shouldn't 2. My grandparents live in the suburb. Therefore, whenever we visit them, we__________a bus. A. must take B. should take C. have to be taken D. have to take 3. We__________smoke on the bus. A. mustn't B. can't C. needn't D. mightn't 4. There are a lot of tickets left, so you__________pay for the tickets in advance. A. mustn't B. won't C. should D. don't have to English 11
