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
대조실험은 과학 연구에서 중요한 방법입니다.daejo silheom-eun gwahak yeongu-eseo jungyohan bangbeob-imnida.A controlled experiment is an important method in scientific research.