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
폴리 염화 비페닐은 환경에 해로운 물질입니다.polli yeomhwa bipehnil-eun hwan-gyeong-e haeroun muljil-imnida.Polychlorinated biphenyl is a harmful substance to the environment.