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
증기기관은 산업 혁명의 중요한 발명 중 하나였습니다.jeung-gi-gigan-eun saneop hyeogmyeong-ui jungyohan balmyeong jung hanaseyo.The steam engine was one of the important inventions of the Industrial Revolution.