1) They were climbing the mountain when he fell off.
2) My dad was waiting for me at 4 pm yesterday.
3) You were having a shower when the telephone rang.
4) I was going home when I had a puncture.
5) The kids were playing in the sands yesterday.
6) You were putting on some warm clothes when I came in.
7) Tom was riding a bike when I saw him.
8) They were cleaning the windows when it started to rain.
9) He was taking notes from 2 to 4 yesterday.
10) Mum was ironing the laundry yesterday afternoon.
11) The students were studying Math yesterday.
12) I was staying with my friend last week.