Ответ:

1. c) rains

2. c) isn't snowing

3. a) Did snow

4. a) is

5. b) are

6. b) the best

7. a) funnier

8. b) stronger

9. b) swam

10. a) was

11. b) weren't

12. b) could/was

13. a) can't speak

14. a) when

15. d) what