Dưới đây là các đáp án phù hợp cho bài tập của bạn:

1. **on** - What will you do **on** Monday?
2. **in** - It is often rainy **in** autumn.
3. **in** - What did you do **in** the afternoon?
4. **at** - I often get up **at** 7 o’clock.
5. **in** - Flowers are beautiful **in** spring.
6. **at** - I watched a new film **at** midnight.
7. **on** - My brother’s birthday is **on** 16th December.
8. **on** - Sam watched a football match on TV **in** the evening.
9. **on** - Do you get presents **on** Christmas Day?
10. **at** - We had lunch **at** noon.
11. **in** - My father was born **in** 1970.
12. **in** - It is very cold **in** winter.
13. **on** - Will you go to the club **on** Friday morning?
14. **on** - What did you do **at** Easter?
15. **on** - We’ll go on a picnic **on** Saturday.

Hy vọng điều này sẽ giúp ích cho bạn!