常見問題：
問：1. Q: What is Secret? 答： A: Secret is a South Korean girl group formed by TS Entertainment in 2009.
問：2. Q: How many members are there in Secret? 答： A: Secret originally had five members, but now consists of only four members after Song Ji-eun's departure.
問：4. Q: What was Secret's debut song? 答： A: Secret's debut song was "I Want You Back," released in 2009.