Question: What singer made appearances during Keith Urban's Ripcord World Tour who also the winner of the  fourth season of "American Idol"?

<P0-S0> An American Idol Christmas (also titled A Very Idol Christmas in Canada) is a Christmas television special for the television shows "American Idol", "American Juniors" and "Canadian Idol", but focused mostly on "American Idol"– the Canadian winner Ryan Malcolm was edited out in the American release, due to legal reasons. <P0-S1>  The special was broadcast on the Fox television network in the United States and CTV in Canada. <P0-S2>  It was first broadcast on November 25, 2003 in the United States. <P0-S3>  It featured some of the top finalists of American Idol's first season (Kelly Clarkson, Tamyra Gray, Christina Christian) and second season (Ruben Studdard, Clay Aiken, Kimberley Locke); "Canadian Idol" winner Ryan Malcolm (not shown in American version due to the upcoming World Idol); and the American Juniors. <P0-S4>  Since the episode was not a competition, none of the judges appeared because they were working on the next season's contestants. <P0-S5>  It was directed by Bruce Gowers, produced by 19 Entertainment, Fremantle Media North America, Cécile Frot-Coutaz, Simon Fuller, David Goffin, Nigel Lythgoe and Ken Warwick. <SEP> <P1-S0>  The Oceania leg of the tour was co-headlined with American singer Carrie Underwood, with Buchanan as opening act. <P1-S1> The Ripcord World Tour (stylized as the ripCORD World Tour) was the eleventh concert tour by Australian singer Keith Urban. <P1-S2>  The tour was in support of his tenth studio album "Ripcord" (2016). <P1-S3>  The tour began on 2 June 2016 in Bonner Springs, Kansas and concluded on 17 December 2016 with two shows in Brisbane, Australia. <P1-S4>  Brett Eldredge, Maren Morris and Dallas Smith were supporting acts for Urban in North America. <SEP> <P2-S0> Carrie Marie Underwood (born March 10, 1983) is an American singer, songwriter, and actress. <P2-S1>  She rose to fame as the winner of the fourth season of "American Idol" in 2005. <P2-S2>  Her debut album, "Some Hearts", was released in 2005. <P2-S3>  Bolstered by the huge crossover success of the singles "Jesus, Take the Wheel" and "Before He Cheats", it became the best-selling solo female debut album in country music history, the fastest-selling debut country album in Nielsen SoundScan history and the best-selling country album of the last 14 years. <P2-S4>  Underwood won three Grammy Awards for the album, including Best New Artist. <SEP> <P3-S0> Harold Elwin "Bo" Bice, Jr. (born November 1, 1975) is an American singer and musician who was the runner-up against Carrie Underwood in the fourth season of "American Idol". <P3-S1>  Prior to auditioning for "American Idol", Bice released a solo album as well as a few albums with his bands while performing in the night club circuit. <P3-S2>  In 2005, Bice charted at number two on the "Billboard" Hot 100 with a rendition of "Inside Your Heaven" from "American Idol". <P3-S3>  He released the album "The Real Thing" after "American Idol" to minor success before being dropped by RCA Records. <P3-S4>  He started his own record label Sugar Money and subsequently released two more albums, "See the Light" and "3". <P3-S5>  As of 2014, he is also the lead singer of the touring version of Blood, Sweat & Tears.