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
음향측심기를 사용하여 바다의 깊이를 측정했습니다.eumhyangcheugsimgireul sayonghayeo badaui gipireul cheugjeonghaessseubnida.We used a fathometer to measure the depth of the ocean.