Question: Age of Youth, is a South Korean television series stars include Ryu Hwa-young, a South Korean singer and actress, and is a former member of which South Korean girl group?
Sentence (from "Kim Chung-ha"): She is best known for finishing fourth in Mnet's girl group survival show "Produce 101" and as a former member of the now disbanded South Korean girl group I.O.I.
Relevant evidence: No