which,,

sarah came to my mother and felt her hair and shoulders. she tried to guess which of her playmates this could be.
이 문장에서끝에 this가 가리키는 것이 무엇인가요? 앞 문장에 sarah came to my mother and felt her hair and shoulders.인가요??그리고 which는 관계 형용사인가요 의문사인가요?~