用所给词的适当形式填空，每空不限一词。

1. I think it's __________ (use) to talk with him. It's difficult to change his mind. 

2. Did you have a nice time __________ (ski) last week? 

3. Our teachers told us that the earth __________ (move) around the sun. 

4. __________ (wolf) eat smaller animals when they are hungry. 

5. __________ (luck), he didn't hurt badly. 

6. His grandpa is ill. He was even __________ (ill) this morning. 

7. When I saw the squirrels, I became __________ (interest) in them. 

8. Can you teach me how __________ (dance)? 

9. I __________ (drive) to Beijing when my car broke down. 

10. Don't leave the baby by __________ (he). It's not safe to leave him alone at home.