Ответ:

1.I was sleeping when my mom came

2.When I arrived the teacher already started the lesson.

3.She was studying from 5 till 10pm yesterday.

4.He bought a new car yesterday.

5.They were recording the song when the lights went out.

6.My brother already leaved when his friend called.

7.The teacher was explaining the matherial and the students were listening him very attentive.

8.I completed the test before the bell ranged.

9.He waited for the train for an hour.

10.She has visited this museum last year.