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
공장폐수는 환경에 큰 영향을 미칠 수 있다.gongjangpaesuneun hwangyeonge keun yeonghyangeul michil su itda.Industrial effluent can have a significant impact on the environment.