어법상 어색한 것을 고르는 문제입니다.

1. is this the pen that you are looking for?
2. judy is the girl who everyone knows.
3. this is the letter which i wrote to her ten years ago.
4. the doll that i bought is very cute.
5. this is the only question which i want to ask you.답이랑 이유 가르쳐주시면 감사하겠습니다..
아무리 봐도 모르겠어요..ㅜ ㅜ