Ответ:

1. saved

2. was walking/saw

3. replied to/received

4. was repairing/was reading

5. gave/told

6. got off/was snowing

7. were increasing

8. were talking/arrived

9. was telling

10. was shivering/feeling ?(might be Past S. as well)

11. was doing

12. whispered

13. had

14. spent

15. began/told

16. moved

17. became

18. was covering/woke

19. fell/was crying

20. were playing/went

21. were travelling

Объяснение:

Some of the sentences are ambiguous and i think several options can be used.