回答

[3]
21. I don't have lunch here.
22. Mari didn't explain the reason.
23. She doesn't read books at home.
24. They didn't send you a card last year.
25. It doesn't rain much here in October.
26. Do you drive a car?
27. Did Mr. Kaneko teach math at school?
28. Does Mike often call you?
29. Did the game start at seven?
30. Did he tell her the story?
[4]
31. Is this your computer? Yes, it is.
32. There was a piano in the room.
33. He speaks English very well.
34. Did she buy the CD? No, she didn't.
35. Open the door.
36. Let's go to the park.
37. It is fine today, isn't it?
38. Hide cooked dinner, didn't he?

主語、be動詞・一般動詞、時制(現在・過去)を考えて疑問文、肯定文、否定文、命令文を作る基本的な練習問題です。
ややこしい内容もありますが、間違いながらでいいので、正しい英文が書けるように練習を続けてください。

この回答にコメントする
疑問は解決しましたか?