Помогите решить упражнение :

In each sentence below one verb is the past simple and the other is in the past continuouns. Put the verbs in the brackets in the right tense.

1. While i was playing the guitar , my string...(break)
2. As we... (drive) home from the party , a police can stopped in front of us.
3. She was painting when she...(spill) water on the table.
4.As i was walking down the street , a little boy... (ask) me for some money