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4. Phuong oughtn’t to eat too much chocolate, or she will gain overweight.
5. We have to wear helmets when she ride a motorbike.
6. I don’t have to book the tickets advance.
7. Alia musnt’t say rude words like that
8. We don’t have to play table tennis, we can play chess instead.
9. Children musn’t put their hands into sockets, that is very dangerous.
10. Doctors sometimes have to work at the weekends and on national holidays.

II/
1. He ought to stop wasting money on lottery.
2. You must finish your homework before going to bed.
3. You don't have to bring food and drink for lunch.
4. You mustn't fish in this park.
5. Every receptionist in our hotel has to wear a uniform.
6. Shops must not sell cigarettes to children.
7. Waiters have to wear a tie.
8. He ought not to drink too much alcohol.
9. Every employee has to keep the company's information secret.
10. I ought to study English to get a good job.