Black Friday: lifetime access is on a special offer in the app, until November 30. Black Friday: special offer on lifetime access, until November 30. Download
호혜성은 사회적 관계를 형성하는 데 중요한 역할을 합니다.hohyeseong-eun sahoejeok gwangyereul hyeongseonghaneun de jungyohan yeoghal-eul hamnida.Reciprocity plays an important role in forming social relationships.