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 중간층은 대기와 맨틀 사이에 위치해 있습니다.jiguui junggancheung-eun daegiwa maenteul sai-e wichihae issseubnida.The middle layer of the Earth is located between the atmosphere and the mantle.