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
지구의 대기권은 생명체가 살 수 있는 환경을 제공합니다.jiguui daegigwon-eun saengmyeongchega sal su itneun hwangyeong-eul jegonghamnida.The Earth's atmosphere provides an environment where living beings can survive.