1. What were you doing... I was playing...
2. ...Were talking...
3. ...Was studying painting.
4. Who were you talking to... I was talking to...
5. Where was he living...
6. Tom was sitting...
7. ...The boys were doing.
8. ...He was saying.
9. While he was learning...
10. ...Mary was practicing the piano.
11. John was working...
12. ...Some of them were bathing in the sea, others were playing...
13. ...He was working...
14. ...While it was going.
15. What was he doing...