Ответ:

1. I was walking to school when it started to rain.

2. I was swimming in the sea when a huge wave hit me.

3. We were doing an exam when the fire alarm went off.

4. I was sitting on the bus when I realized I left my phone at home.

5. I was skiing when I fell and twisted my ankle.

6. I was talking on my phone when the battery died.

7. I was eating a burger when my friend told me some bad news.