Question: In between Joe Elliott and Yuju, who was a South Korean singer?
Context: Choi Yu-na (born October 4, 1997), better known by her stage name Yuju, is a South Korean singer.  She is best known as the main vocalist of the South Korean girl group GFriend. 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). Richard "Rick" Savage (born 2 December 1960) is the bass guitarist and one of the founding members of the English rock band, Def Leppard.  He is called "Sav" to avoid confusion between him and the other Rick in the band, drummer Rick Allen.  Savage and lead singer Joe Elliott are the only remaining original members of the band.  The two of them, plus Allen, are also the only members of the band who have performed on every album. Kim Tae-yeon, better known by the mononym Taeyeon, is a South Korean singer.  Her discography consists of one studio album, two extended plays (EPs), twenty singles (including four as featured artist), and three promotional singles.  She debuted as a member of South Korean girl group Girls' Generation in August 2007 and initially gained some popularity as a singer upon recording soundtrack songs "If" for "Hong Gil Dong" and "Can You Hear Me" for "Beethoven Virus" (2008).  She subsequently established herself as one of the most renowned vocalist on the South Korean music scene with further soundtrack recordings, notably "I Love You" for "" (2010), "Missing You like Crazy" for "The King 2 Hearts", "Closer" for "To the Beautiful You" (2012), and "And One" for "That Winter, the Wind Blows" (2013), all of which managed to enter the top ten of South Korea's Gaon Digital Chart.  Apart from soundtrack recordings, Taeyeon has also recorded duets with other artists, most notably "Like a Star" with The One and "Different" with Kim Bum-soo, which peaked at numbers one and two on the Gaon Digital Chart, respectively. "Hysteria" is a love song by the English hard rock band Def Leppard.  It is the tenth track on their 1987 album of the same name and was released as the third single from that album in November 1987.  On "VH1 Storytellers: Def Leppard", lead singer Joe Elliott revealed that the song title came from drummer Rick Allen. Atomic Mass was an English hard rock/heavy metal band from Sheffield, who formed in 1977 as part of the new wave of British heavy metal movement.  The group's core members along with newly recruited singer Joe Elliott later became Def Leppard, eventually becoming one of the UK's top-selling hard rock bands. Joseph Thomas Elliott Jr. (born 1 August 1959) is an English singer-songwriter and musician, best known as the lead singer of the English rock band Def Leppard.  He has also been the lead singer of the David Bowie tribute band the Cybernauts and the Mott the Hoople cover band Down 'n' Outz.  He is one of the two original members of Def Leppard and one of the three to perform on every Def Leppard album. GFriend (Hangul: 여자친구 ; RR: "Yeoja Chingu " ) is a six-member South Korean girl group formed by Source Music in 2015.  The group consists of Sowon, Yerin, Eunha, Yuju, SinB, and Umji.  They made their debut with the EP "Season of Glass" on January 16, 2015.  GFriend won several 2015 female rookie awards and has garnered momentum since their debut, despite coming from a small company.  In 2016, they continued their success with their third EP "Snowflake" and won first place on many music shows with the title song "Rough".  They released their first full-length album "LOL" in July 2016. 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. "Bringin' On the Heartbreak" is a ballad originally recorded by British hard rock band Def Leppard.  It was the second single from their 1981 album "High 'n' Dry".  The song was written by three of the band's members: Steve Clark, Pete Willis, and Joe Elliott.  In 2002, it was covered by American R&B/pop singer Mariah Carey for her album "Charmbracelet".  Many reviews of the R&B cover were positive, as was the reaction from Def Leppard's Joe Elliott.
Answer: Choi Yu-na