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
부운유설은 자연 현상을 설명하는 데 사용됩니다.buwonyuseoreun jayeon hyeonsangeul seolmyeonghaneun de sayongdoemnida.The theory of the floating cloud is used to explain natural phenomena.