1. Why has he stopped?
2. is looking for, hasn't found
3. It is
4. What are you studying now?
5. They have just given
6. She is knitting
7. Are you having only a piece of cake? You're not eating much
8. are planting
9. are going
10. who has finally found; is giving
11. are you sick
12. Have you seen
13. are you looking
14. is looking
15. is going; isn't going
16. Hasn't leaved
17. have payed
18. Have known
19. is making
20. is doing and taking
21. am having
22. Has never traveled