The document provides a list of rules and instructions that use the modal verb "must" or "mustn't" to convey obligations and prohibitions. Some of the rules include studying hard, learning English, listening to the teacher, not smoking, not being late for school, not walking on the grass, being quiet, not making noise, and putting rubbish in the bin.

1. You must study hard.

2. We must learn English .

3. They must listen to the teacher.

4. He mustn’t smoke.

5. You mustn't be late for school.

6. You mustn't walk on the grass .

8. We ... be quiet.

9. We must be quiet.

10. You …….. make noise in this area.

11. You mustn’t make noise in this area.

12. We ... eat sweets in the classrooms.

13. We mustn’t eat sweets in the classrooms.

14. You ... put the rubbish into the bin.

15. You must put the rubbish into the bin.