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
중력댐은 물의 압력을 이용하여 안정성을 유지합니다.jungnyeokdaemeun mureul aplyeogeul iyonghayeo anjeongseong-eul yujihamnida.A gravity dam maintains stability by using the pressure of water.