Решение:
- We were talking loudly when our teacher came in. (talk)
- Dad was running when I saw him in the park. (run)
- The dog was playing happily when it started to rain. (start)
- I was doing the exercise when the teacher came to my desk. (do)
- I was answering the nurse politely when the doctor came in. (come)
Ответ: 1. were talking loudly, 2. was running, 3. happily, 4. was doing, 5. politely