Here are the matched sentences and answers based on the provided prompts:

1. break / play / basketball / time.
**Answer:** "I play basketball."

2. library / What / is / colour?
**Answer:** "What is the colour of the library?"

3. ruler / What / is / its / colour?
**Answer:** "What is the colour of the ruler?"

4. cooking / like / and / singing.
**Answer:** "I like cooking and singing."

5. old, / eight / years / am / I.
**Answer:** "I am eight years old."

6. This / is / Ms. Huong / teacher, / my.
**Answer:** "This is my teacher, Ms. Huong."

7. open / May / I / book?
**Answer:** "May I open the book?"

8. eye. / is / an / I.
**Answer:** "I have an eye."

9. What / you / do / (do) / break?
**Answer:** "What do you do to break?"

10. I / basketball / play / at / break?
**Answer:** "Do I play basketball at break?"

11. What / is / colour / your / pen?
**Answer:** "What is the colour of your pen?"

12. My / is / pen / black. / It.
**Answer:** "My pen is black. It is."

13. Let’s / to / go / the / room / music?
**Answer:** "Let’s go to the music room."

14. What / are / your / colour / pencil cases?
**Answer:** "What are the colours of your pencil cases?"

15. My / are / pencil cases / blue. / They.
**Answer:** "My pencil cases are blue. They are."

16. He / plays / badminton / at / time.
**Answer:** "He plays badminton at times."

17. May / I / open / book / the?
**Answer:** "May I open the book?"

18. May / I / go / out?
**Answer:** "May I go out?"

19. Yes / can / you?
**Answer:** "Yes, you can."

20. We / play / basketball / playground / in / the / at / break / time.
**Answer:** "We play basketball in the playground at break time."

21. Write the missing letter:
**Answer:** Fill in the appropriate missing letters as needed based on context.

Feel free to ask if you need anything else!