Was walking, began
were you reading
was digging, hurt
was waiting
was she driving, happened
4.
they were having a conference yesterday at 5 pm.
We were laying a table when the guests arrived
I was asleep when I heard somebody knocking the door.
He was walking along the road when he slipped on the banana peel. Mother was cooking while I was doing my home work. He was reading a contract when his boss called.