Ex.1
1. leaves
2. is leaving
3. watch
4. are sitting, are watching
5. does
6. is doing
7. rains
8. is raining
9. has
10. is having
ex.2
1. played
2. was playing
3. played
4. were playing
5. was Nick doing
6. were you doing
7. didn't sleep
8. did he do, read
9. was he doing, was reading
10. was she sleeping
ex. 4
1. is
2. are
3. are
4. is
5. are