Odpowiedź:
1. cheat in *tests*
2. return your library books on *time*
3. study for your *exams*
4. use your *mobile*
5. return your library books *late*
6. change your *shoes*
7. *drop* litter
You must:
- return your library books on time
- study for your exams
- change your shoes
You musn't:
- cheat on tests
- use your mobile
- return your library books late
- drop litter
