1. I caught that cold when I was skating on a frosty day.
2.  He wrote those nice poems when he was having a holiday.
3. She learnt the language when she was living in England.
4. She heard that song when she was listening to a concert on the radio.
5.  I bought that book when I was reading up for my exams.
6.  The boy hurt himself when he was riding the bicycle.
7.  Philip lost his camera when he was walking about the city.
8.  He rang you up when he was having supper.