Ответ:

1. She was busy.

2. I wasn't busy.

3. Were you busy?

4. Were they at home?

5. He wasn't at home.

6. I didn't know.

7. Did they know?

8. She didn't know.

9. Who knew?

10. Nobody knew.

11. Did he read English books?

12. They never read.

13. Did she have a flat?

14. She didn't have anything.

15. Who was that?