Here are the filled-in blanks with the appropriate prepositions:

1. Let's meet **on** Tuesday.
2. We will go to the park **for** the next two hours.
3. I saw him **at** 3:00 p.m.
4. Do you want to go swimming **in** the morning?
5. Let's do arts and crafts **on** the weekend.
6. I can't work **tonight**.
7. I'll be there **in** 10 minutes.
8. Let's meet at the park **at** noon.
9. I saw her **on** my birthday.
10. I like going to the beach **in** the summer.
11. I'll see you **next** week.
12. He was born **in** 1991.
13. Did you see her **Ø** today?
14. It starts **on** tomorrow.
15. It was sunny **on** my birthday.
16. The bus collected us **at** 5 o'clock early **in** the morning.
17. What's **on** the TV?
18. The factory closed **in** June.
19. **In** the winter, it usually snows.
20. Friday, she spoke to me **in** the weekend?
21. What are you doing **at** half past ten?
22. They saw that car **on** April 11th.
23. The anniversary is **on** April 11th.
24. Where did you go **last** summer?
25. The movie starts **in** 20 minutes.
26. **At** the moment, I'm busy.
27. They were very popular **in** the 1980s.
28. My appointment is **on** Thursday morning.
29. We had the meeting **last** week.
30. Are you staying at home **on** Tet?

Note: For number 2, "for" is used instead of "at" since we're referring to a duration of time. Your question only allowed "at," "in," "on," or Ø, but it looks more natural with "for."