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
우리는 새로운 비행기를 테스트하기 위해 풍동을 사용했다.urineun saeroun bihaenggireul teseuteuhagi wihae pungdong-eul sayonghaetda.We used a wind tunnel to test the new airplane.