Ex.1
1. snows 2. is snowing 3. cooks 4. is cooking 5. leaves 6. is leaving 7. watch 8. are sitting; are watching 9. does 10. is doing 11. rains 12. is raining 13. has 14. is having
Ex.2
1. goes 2. are watching 3. writes 4. drives 5. is sitting 6. is ringing 7. studies 8.spend 9. go 10. is riding
Ex.3
1. aren't 2. don't 3. isn't 4. am not 5. doesn't 6. isn't 7. doesn't 8. don't 9. don't 10. doesn't