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 자기장은 우리가 나침반을 사용할 수 있게 해줍니다.jiguui jagijangeun uriga nachimban-eul sayonghal su itge haejumnida.The Earth's magnetic field allows us to use a compass.