Odpowiedź:
2. The actors were on stage but they weren't performing (not/preform).
3. The teacher was checking(check) student's tests all afterroom.
4. They were listening(listen) to a live concert when we arrived.
5. It was noon, so the kids were having (have) lunch in the school canteen.
6. What was the mechanic doing (do) in the garage?
Jest dobrze, licze na naj :))