第三产业在城市化的动力机制中为：

A．初始动力

B．根本动力

C．后续动力

D．持续动力

用am,is,are填空。

1  Excuse me! _____ this your eraser?

2. What  _____ those?  _____ they birds?

3. This  _____ his ruler. Where  _____ my ruler?

4. I  _____ in Class Three.  _____ you in Class Three,too?

5. _____ these her English books?

6. Those  _____ their apples. Where  _____ his apples?

7. She  _____ eleven. How old  _____ that boy?

8. He  _____ my friend.  _____ your friend a boy or a girl?

9. _____ those maps? No,they  _____ not. They  _____ pictures.

10. These  _____ your bananas. Here you  _____ .