5. Complete the sentences with must/ mustn't or have/has to/ don't/doesn't have to
1. You___________ study harder to get better marks
2. The boy is only twelve years old. He___________ ride a motorbike.
3. You___________worry about me! I am ok now.
4. All the students___________ obey the school rules.
5. You___________ be impolite to elderly people.
5. Secretaries___________ answer the phone. That is a part of their job.
7. Hoang and My are on holiday. They___________ go to school today
8. He___________ come if he doesn't want to join with us.
9. My classmate is very ill. She___________ see a doctor as soon as possible.
10. Your hands are dirty. You ___________ wash them before meal.
11. We___________ brush our teeth at least once a day.
12. I___________ take these books back to the school library on time or I will get a fine.
13. Children___________ play with dangerous objects like knives and matches.
14. Students___________ use mobile phones during the test.
15. Today she doesn't have the literature lesson, so she___________bring her literature book.
16. Babies___________ go to bed early.
17. There is a lift in this building, so we___________ climb the stairs.
18. Huong doesn't like her new job. Sometimes she___________ work at weekends.
