4. 他们可以在课堂上自由交谈。

3. 但在美国，情况大不相同。

2. 在课堂上，他们总是仔细听讲，认真做笔记。

1. 中美课堂有些不同。

5. You must be careful with your things.

      with your things.

4. Will you please read it again?  

       again,please.

3. You can't go to bed late.

      to bed late.

2. You shouldn't play football on the street. It's dangerous.

       on the street. It's dangerous.

1. If you don't listen carefully,you will hear noth?ing.

       carefully,you will hear nothing.

(   ) 8. —What are the rules at your school?

―Don't run in the hallways and       arrive late for class.

   A. not to   B. won't

   C. don't   D. no