Which South Korean singer/actress was a member of both DIA and I.O.I?
Jung Chae-yeon: Jung Chae-yeon (born December 1, 1997), better known by the mononym Chaeyeon, is a South Korean singer and actress. Jung Chae-yeon:  She is best known for being a member of the South Korean girl group DIA, and for finishing 7th in the survival show "Produce 101", making her a member of I.O.I.
i don't know