가 쓴

… wrote

→ 가
phrase Common #3,124
… wrote 가 marks the subject, and 쓴 describes a noun that follows: 네가 쓴 책 means “the book you wrote.”
KO: 민수가 쓴 편지를 읽었어요.
EN: I read the letter Min-su wrote.

크리스띠나가 쓴 거 다

Christina wrote it.

— 산딸기 (1957)

산티아고가 쓴 편지 예요

This is a letter written by Santiago.

— 어 퓨 굿 맨 (1992)

정말 미마가 쓴 것 맞아?

Is this really what Mima wrote?

— 퍼펙트 블루 (1998)