Ответ:

1. You were sleeping when i came home.

2. He was reading on the sofa when I entered room.

3. I was walking along the street with my friend when tram passed.

4. She was looking out of window when i saw her.

5. We were answering the teacher`s question when the head teacher entered the classroom.

6. They were drinking tea when i returned home.

7. He was walking along the river when it started to rain.

8. The old man was thinking about the plan when the phone rang.

9. We were listening to an interest lection yesterday.

10. When i entered the classroom, the teacher was writing some words on the board and pupils was coping them into their exercise books.