1. don't know

2. Do they want

3. thinks, drives

4. understands, eats, forgets

5. Who is that man who is standing in the doorway? - Don't you recognize him? It is John, my cousin.

6. have, am having

7. Does your family leave, go, like, stays, returns

8. Where are Tom and Nick, are having

9. What are you doing, are listening

10. Do you want to see my father? - Yes, I do.

11. knows, wants, has