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
석탄의 건류 과정은 많은 에너지를 생성합니다.seoktan-ui geollyu gwajeong-eun manh-eun enejileul saengseonghamnida.The process of destructive distillation of coal generates a lot of energy.