Исправить ошибки в предложениях:

1. Does it often snow in winter?
2. I have never met him.
3. I have been cleaning my room for two hours. 
4. She is cooking... 
5. Those girls translated... 
6. She haven't finished... 
7. They discussed everything two days ago. 
8. He is not swimming.
9. I think that... 
10. ...for ten hours.