Помогите!!!! Не можем понять.

1 You mustn't run.

2 You must listen to the teacher.

3 You must write.

4 You must open the book.

5 You mustn't drink cola.

6 You mustn't jump.

7 You mustn't close the book.

8 You must read.

9 You mustn't play football.

10 You must clean the board.

11 You mustn't draw on the desk.

12 You mustn't shout.

13 You mustn't talk on the mobile phone.

14 You must do your homework.