Вопрос по английскому языку:

Complete the sentences with the correct forms of the verbs.
1)when he came home he____ (to read)an interesting story about the animals.

2)Kate entered the classroom when John____ (to stand) at the blackboard.

3)When his mother returned home he___ already (to do) his home exercises.

4)asel liked to listen to pop-music when she ___ (to be) younger.