1. are skating
2. Did you skate .... Yes, we were skating
3. He skates
4. What are you doing now? — I am washing the dishes.
5. What were you doing at three o'clock yesterday? — I was having dinner.
6. Are you having
7. Where does your brother work? — He works at an institute.
8. Was your grandmother sleeping when you came home yesterday?
9. What will your brother do tomorrow?
10. I did not go to the shop yesterday. I will go to the shop tomorrow.
11. Where was Kate going when you met her yesterday?
12. Every day the boss enters the office at nine o'clock.
13. Entered
14. When will the secretary come tomorrow?
15. At six o'clock yesterday we were listening to a very interesting lecture.
16. When I entered the office, the secretary was typing some letters.
17. My friend rang me up at eight o'clock yesterday.