Jung Chae-yeon (born December 1, 1997), better known by the mononym Chaeyeon, is a South Korean singer and actress.
 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.
Cho Seung-hee (born June 3, 1991) is a South Korean actress and singer.
 She was a member of South Korean girl group F-ve Dolls and DIA.
 She has participated in various television dramas such as "Mr. Back" (2014), "Triangle" (2014), "The Night Watchman's Journal" (2014) and "The Producers" (2015).
Han Sun-hwa (born October 6, 1990), is a South Korean singer and actress.
 She is a former member of the South Korean girl group Secret.
 She made her television debut in 2004 while participating in SBS's "Superstar Survival" as a finalist, and in 2009, she was a regular cast on a variety show called "Invincible Youth".
 Aside from music, she also ventured into acting and made her debut in the 2010 drama, "More Charming By The Day".
 She also acted in several dramas with supporting roles in "Ad Genius Lee Tae-baek", "God's Gift - 14 Days", and "Marriage, Not Dating".
 In 2014 she finally starred as a lead actress on MBC's weekend drama "Rosy Lovers" as Baek Jang Mi co-starring with actor Lee Jang Woo.
 CNN International Seoul listed Sunhwa as one of the nine rising "It" stars in Korean entertainment citing her as a "multi-tasking" artist.
 Her portrayal of Kang Se-Ah in the 2014 TVN drama, "Marriage, Not Dating" earned her a nomination for "Best Youth Actress" at the 16th Seoul International Youth Film Festival.
 In 2014, her portrayal of Jang-Mi from "Rosy Lovers" and Jenny from "God's Gift 14 Day"s won her two best new actress awards from MBC and SBS Drama Awards.
 It was confirmed on September 26, 2016 that Sunhwa had not renewed her contract with TS Entertainment and will officially part ways in October.
 On October 14, 2016 Sunhwa joined Huayi Brothers as an actress.
I.O.I (; also known as IOI or Ideal of Idol) was a South Korean girl group formed by CJ E&M through the 2016 reality show "Produce 101" on Mnet.
 The group was composed of eleven members chosen from a pool of 101 trainees from various entertainment companies: Lim Na-young, Kim Chung-ha, Kim Se-jeong, Jung Chae-yeon, Zhou Jieqiong, Kim So-hye, Yu Yeon-jung, Choi Yoo-jung, Kang Mi-na, Kim Do-yeon and Jeon So-mi.
 They debuted on May 4, 2016 with the EP "Chrysalis" and actively promoted as a whole and as a sub-unit for less than a year.
Sunmin (Hangul: 선민, "Katakana": ソンミン, born August 4, 1987) is a South Korean singer who speaks and sings in Korean, Japanese, and English.
 She debuted in 2006, with the single "Keep Holding You," a collaboration with the Japanese R&B singer Toshinobu Kubota.
 Her career was initially focused on the Japanese market, but her work became focused in South Korea from 2009 to 2010.
 She also contributed to original soundtracks of South Korean television series "Master of Study" and "Gloria (2010 TV series)".
 In 2010 to 2011, she was in the main South Korean musical production of "Jekyll & Hyde" as Lucy.
 In 2012 to 2013, she reprised her role as Lucy in the South Korean national tour.
 In spring 2013, Sunmin played Josephine in the South Korean production of "Arsène Lupin", the musical.
Ji Hye-ran (born January 3, 1996), better known by her stage name Z.Hera, is a South Korean singer and actress.
 Z.Hera appeared on the documentary program "Human Theater" in 2006 as Shaolin Girl when she was 11 years old.
 She received attention after being the first South Korean singer to appear on the American social site BuzzFeed.
 She is known for her roles in "Moorim School" (2016) and "" (2016).
Kwon So-hyun (born August 30, 1994), is a South Korean singer and actress.
 She was known as a member of the South Korean girl group 4Minute, under Cube Entertainment.
 She is also a former member of the South Korean girl group, Orange.
 Before June 15, 2016 (end of her contract with Cube), Sohyun left 4Minute and the record label along with members Nam Ji-hyun, Heo Ga-yoon, and Jeon Ji-yoon.
Lee Ji-yeon (born February 18, 1984), better known by her stage name Lina is a South Korean singer and musical actress.
 She debuted in 2002 as a member of South Korean R&B duo Isak N Jiyeon and disbanded in 2004.
 She later re-debut as a member of South Korean girl group The Grace in 2005 and the group currently being inactive.
 She currently active as a musical actress.
Ki Hui-hyeon (born June 16, 1995), better known by the mononym Huihyun and former stage name Cathy, is a South Korean singer.
 She is best known as a member of the South Korean girl group DIA.
Dia (Hangul: 디아, stylized as DIA) (born June 12, 1992) is a South Korean singer and a member of the disbanded girl group Kiss&Cry.

Question: Which South Korean singer/actress was a member of both DIA and I.O.I?
Answer: Jung Chae-yeon