ex 4:
2. mustn't go
3. musn't get up
4. must help
5. mustn't stay
6. must watch
7. must tell
8. must remember
ex 5:
2. You should get more sleep or you'll fall asleep in the Maths class
3. You must concentrate more in your classes or your teacher will find out this.
4. You musn't go to bed late this evening or you'll be very tired tomorrow.
5. You should get a snack otherwise you'll still get hungry.
6. Yoh should tell her that you'll call her later because now you're doing your homework
