用所给词的适当形式填空。

1. How many _____ (email ) do you get?

2. He is always the _____ (one ) one to get to school.

3. Thanks for giving me some _____ (information).

4. Sometimes my father _____ (buy) tickets on the internet.

5. Do they _____ (go) online in the evening?

6. Tom and Linda are the old man's _____ (grandchild).

7. Jim _____ (not have) breakfast at home.

8. Can you _____ (open) a new document?

9. The little boy _____ (switch) on the lights and goes into the room.

10. I want _____ (close) the window.

为什么要限制飞机重心位置？