1. At this time last year, they (build)were building this house.

2. I (drive)was driving my car very fast when you called me.

3. I (chat)was chatting with my friends while my teacher (teach)was teaching the lesson yesterday.

4. My father (watch)was watching TV when I got home.

5. At this time yesterday, I (prepare)was preparing for my son's birthday party.

6. What were you (do)doing at 8 pm yesterday?

7. Where were you (go)going when I saw you last weekend?

8. They (not go)weren't going to school when I met them yesterday.

9. My mother (not do)wasn't doing the housework when my father came home.

10. My sister (read)was reading books while my brother (play)was playing football yesterday afternoon.

1. were building

2. was driving

3. was chating/was teaching

4. was watching

5. was preparing

6. were you doing...

7. were you going..

8. were not going

9. was not doing

10. was reading/was playing