1) When I came home, my little sister was sleeping.

2) When Nick came home, his brother was playing with his toys.

3) When mother came home, I was doing my homework.

4) When father came home, Pete was sleeping.

5) When mother came home, the children were playing on the carpet.

6) When I got up, my mother and father were drinking tea.

7) When I came to my friend's place, he was watching TV.

8) When I saw my friends, they were playing football.

9) When I opened the door, the cat was sitting on the table.

10) When Kate opened the door, the children were dancing round the fir-tree.

11) When Tom was crossing the street, he fell.

12) When I was going to school, I met my friend.

13) When we were going to the cinema, we met grandfather.

14) When grandmother was going home, she saw many children in the yard.

15) When Henry was walking about in the forest, he found a bear club.

В первых 10ти предложениях в первой части стоит Past Simple, во второй - Past Continious. В последних 5ти ситуация противоположная.