=>

20. Clean your bed room more regularly or you will get a breathing problem.

-> or: nếu không

21. I was standing right next to her, but she didn't recognize me.

-> but: nhưng

22. The road was slippery, so they couldn't drive fast.

-> so: vì vậy, vậy nên

-> couldn't V: không thể làm gì

23. If you didn't work too fast, you wouldn't make so many mistakes.

-> câu đk loại 2: If S V2/ed, S would (not) V (không có thật ở hiện tại)

24. People admire him because he has talent.

-> because S V: bởi vì

25. It's a good idea to eat different kinds of fruit and vegetables every day.

-> it's a good idea to V (~ nó là một ý kiến hay để làm gì)

26. My brother doesn't like ice-skating because he thinks it is dangerous.

-> because S V: bởi vì

Đáp án + giải thích:

20. → Clean your bed room more regularly or you will get a breathing problem.

→ ...or + S + will....: ...nếu không....sẽ....

21. → I was standing right next to her, but she didn't recognize me.

22. The road was slippery, so they couldn't drive fast.

→ so: vì vậy nên

→ couldn't + V: không thể làm gì

23. If you didn't work too fast, you wouldn't make so many mistakes.

→ câu điều kiện loại 2: cấu trúc: If + S + V2/ed, S + would (not) + V 

24. People admire him because he has talent.

→ Cấu trúc: ...because + S + V

25. It's a good idea to eat different kinds of fruit and vegetables every day.

→ Cấu trúc: It's a good idea to + V 

26. My brother doesn't like ice-skating because he thinks it is dangerous.

→ because + S + V: bởi vì....