Do Kyung Soo (도경수) or people knows as D.O. is member South Korean boyband EXO-K, EXO Korean subgroup. He was winning in a singing competition and cast into S.M. Entertainment through the S.M. Casting System in 2010. Before auditioning SM, he took up vocal lessons and such even. On January 30, 2012 D.O. was formally introduced as a EXO-K member. On February 24, 2012 D.O. appeared in the EXO trailer. Prolog single "What Is Love" is sung only by D.O. and Baekhyun, released on January 30, 2012.