Ответ:

1. They translated a difficult text yesterday.

2. I was opening the window six o'clock yesterday.

3. Did you go to the cinema yesterday?

4. I didn’t see Mike last week.

5. When I opened the door, my friends were siting around the table.

6. When did you begin doing your homework yesterday?

7. We were discussing the latest news from three till four yesterday.

8. When I was reading the newspaper yesterday, I found an interesting article on UFOs.

9. Lena swept the floor on Sunday.

10. Lena was sweeping the floor from eleven till twelve on Sunday.

11. They did go to the wood last Sunday?

12. When they were sailing down the river they saw a little island.

13. We were working the whole morning yesterday.