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
지질학적 연구는 지구의 구조를 이해하는 데 중요하다.jijilhakjeok yeonguneun jiguui gujoreul ihaehaneun de jungyohada.Geological research is important for understanding the structure of the Earth.