N5
1) I was talking to my friend when doorbell rang.
2) They were playing football when it began raining.
3) Jeff was reading a magazine when the TV show started.
4) Sue was having a cup of tea when the doorbell rang.
5) We were walking our dog when it began raining.
6) You were having lunch when the TV show started.
7) The children were enjoying the game when it became dark.
N6.
1) Mum was watching a film when we decided to have some tea.
2) We were preparing for the party when our visitors tang at the door.