1. They were drinking  tea when I came home.
2. He was walking along the river when a boat passed.
3. The old man was thinking  about his plan when he  fell asleep.
4. We  listened to an interesting lecture yesterday.
5. When I  entered the classroom, the teacher was writing words on
 he blackboard and the pupils were  coping  them into their exercise-books.
6. They were getting  ready to go out when it began raining.
7. Yesterday at one o'clock I had  lunch at the canteen.
8.When he came in, I was doing  my exercises.
9. What did you do at eight o'clock yesterday?
10.At this time yesterday I was going  home.
11. You were sleeping  when I went out.
12. He was reading  on the sofa when I came in and sat down beside him.
13. I was walking  along the street with my friend when a tram  passed.
14. She was looking out of the window when I saw her.
15. We were  answering  the teacher's questions when the headmistress entered the classroom.