Complex sentence: On December 29,2011, he became the fourth member to be formally introduced as an EXO member to the public, alongside Luhan, Tao and Kai at 2011' SBS Gayo Daejeon.
Split into simpler sentences: On December 29,2011, he was formally introduced as the fourth member of EXO. He made first appearances as Exo member to the public, alongside Luhan, Tao and Kai at 2011' SBS Gayo Daejeon.