1. Fill in: at, in, on.

Решение:

1. I sometimes work on Sunday.
2. The school starts at 8 o'clock.
3. It's very cold in winter.
4. I wake up at 6 o'clock.
5. I was born on 1 April, 1993.
6. I watch TV in the evening.
7. I go to the sea in summer.