Question: Which American singer was part of the Citizen Change political service group and spent a record sixteen weeks atop the "Billboard" Hot 100.
Context: The "Billboard" Hot 100 is a chart that ranks the best-performing singles of the United States.  Its data, published by "Billboard" magazine and compiled by Nielsen SoundScan, is based collectively on each single's weekly physical and digital sales, as well as airplay and streaming.  At the end of a year, "Billboard" will publish an annual list of the 100 most successful songs throughout that year on the Hot 100 chart based on the information.  For 2005, the list was published on December 20, calculated with data from December 4, 2004 to November 26, 2005.  The R&B track We Belong Together by American singer Mariah Carey was named the number 1 song of 2005 and it spent the longest time at number 1 for the year, 14 weeks.  This is also the joint-second longest time at number 1 for a single in the 57-year history of the Hot 100 post-1958 inception, after Mariah Carey's own collaboration with Boyz II Men, One Sweet Day, which spent 16 weeks atop the Hot 100 from 1995 to 1996. Citizen Change is a political service group, founded by musician P. Diddy, and backed by Mary J. Blige, Mariah Carey and 50 Cent.  The stated aim was to get young people to vote. American singer Madonna has released 83 singles and 16 promotional singles, and charted with 14 other songs.  In 1982, she signed a contract with Sire Records and Warner Bros.  Records, and released her first two singles before launching her eponymous debut album.  Her first entry on the US "Billboard" Hot 100 was "Holiday" (1983), which peaked at number 16.  The following year, Madonna released "Like a Virgin", which reached number one in Australia, Canada and the US; in the latter it spent six weeks atop the chart.  The album "Like a Virgin" spawned three other top five singles: "Material Girl", "Angel", and "Dress You Up".  In 1985, Madonna released her second US number-one single, "Crazy for You", and her first UK number-one single, "Into the Groove", both from feature film soundtracks.  The following year, her third studio album "True Blue" gave her three number-one singles: "Live to Tell", "Papa Don't Preach", and "Open Your Heart".  Two other singles from the album, "True Blue" and "La Isla Bonita", were top-five hits.  In 1987, she scored another number-one single with "Who's That Girl".  The title track from Madonna's fourth studio album, "Like a Prayer" (1989), was her seventh single to top the Hot 100 chart, making her the female artist with the most number-one singles in the 1980s (shared with Whitney Houston). "When I'm Gone" is a song by American rock band 3 Doors Down.  It was released in October 2002 as the lead single from their second album, "Away from the Sun".  It peaked at  4 on the "Billboard" Hot 100 chart in April 2003.  The song also spent seventeen weeks atop the "Billboard" Hot Mainstream Rock Tracks chart from November 2002 through March 2003, becoming one of the longest-running number-one singles on that chart.  The song also peaked  2 on the Hot Modern Rock Tracks chart almost reaching  1 by one spot from Queens of the Stone Age's "No One Knows" on the issue dated February 15, 2003.  It spent one week atop the Top 40 Mainstream chart for one week on May 3, 2003 and also peaked at  3 on the Adult Top 40 chart. Songbird is a studio album by Barbra Streisand, released in 1978.  The album includes Streisand's solo version of "You Don't Bring Me Flowers".  She also subsequently recorded this song as a duet with Neil Diamond and this version topped the "Billboard" Hot 100 chart for two non-consecutive weeks in December 1978.  The title track reached number 25 on the Hot 100 and spent two weeks atop the adult contemporary chart. "How Deep Is Your Love" is a pop ballad written and recorded by the Bee Gees in 1977 and released as a single in September.  It was ultimately used as part of the soundtrack to the film "Saturday Night Fever".  It was a number three hit in the United Kingdom and Australia.  In the United States, it topped the "Billboard" Hot 100 on 24 December 1977 (becoming the first of six consecutive US number-one hits), ended the 10-week reign of Debby Boone's "You Light Up My Life" and stayed in the Top 10 for a then-record 17 weeks.  The single spent six weeks atop the US adult contemporary chart.  It is listed at number 22 on the 55th anniversary edition of "Billboard's All Time Top 100".  Alongside "Stayin' Alive" and "Night Fever", it is one of the group's three tracks on the list.  The song was covered by Take That for their 1996 "Greatest Hits" album, reaching number-one on the UK Singles Chart for three weeks. Numb is a song by American rock band Linkin Park.  It was released as the third single from their second studio album, "Meteora" (2003), and is the thirteenth and final track on the album.  One of Linkin Park's most well-known and critically acclaimed songs, "Numb" topped the "Billboard" Alternative Songs chart for 12 weeks.  The song spent six weeks at the top of the chart in 2003 and six weeks in 2004.  The song also spent three weeks atop the "Billboard" Hot Mainstream Rock Tracks chart and peaked at number 11 on the "Billboard" Hot 100. The discography of MercyMe, an American Christian rock band, includes nine studio albums, two compilation albums, two video albums, and 24 singles.  MercyMe, formed in 1994, released six independent albums from 1995–2000 before signing with INO Records and releasing their major label debut album, "Almost There" (2001).  "Almost There" peaked at number 37 on the "Billboard" 200 and number one on the "Billboard" Christian Albums chart.  The band released "Spoken For", their second studio album, in 2002; it peaked at number two on the "Billboard" Christian Albums chart and number 41 on the "Billboard" 200.  Its second single, "Word of God Speak", spent a record 23 weeks atop the "Billboard" Christian Songs chart.  The album has been certified Gold by the Recording Industry Association of America (RIAA), and has sold over 550,000 copies.  In 2003, mainstream radio interest in "I Can Only Imagine", the band's second single from "Almost There", caused sales of the album to surge.  "I Can Only Imagine" would peak at number five on the "Billboard" Adult Contemporary chart and number 71 on the "Billboard" Hot 100.  "Almost There" was eventually certified double Platinum by the RIAA, signifying shipments of over 2,000,000 copies, and has sold over 2.2 million copies in the United States. American-Canadian singer Robin Thicke has released seven studio albums, twenty-six singles and twenty music videos.  Thicke signed his first recording contract with Interscope Records as a teenager and found success as a songwriter, before he began concentrating on his career as a performer.  In 2000, Thicke started recording his debut album, "A Beautiful World", which was released in April 2003.  The album debuted at number 152 on the US "Billboard" 200, selling 119,000 copies.  The record also peaked at number 36 on the Mega Album Top 100 in the Netherlands.  Two singles were released from the album; the first, "When I Get You Alone" became a top ten hit in the Netherlands and New Zealand.  That single also peaked at number 17 in Australia and was certified gold by the Australian Recording Industry Association (ARIA).  In 2006, Thicke released his second studio album "The Evolution of Robin Thicke".  The record debuted at number 5 on the US "Billboard" 200, topped it on the "Billboard"'s Top R&B/Hip-Hop Albums, and became a certified platinum by the Recording Industry Association of America (RIAA).  The album also charted in France, the Netherlands, and the United Kingdom.  "The Evolution of Robin Thicke" produced four singles, all of which charted on the "Billboard"'s Hot R&B/Hip-Hop Songs. " Lost Without U" became one of his biggest hits, peaking at number 14 on the US "Billboard" Hot 100 and spending 11 weeks atop the "Billboard"'s Hot R&B/Hip-Hop Songs. Mariah Carey (born March 27, 1969 or 1970) is an American singer, songwriter, record producer, and actress.  In 1990, she rose to fame with the release of "Vision of Love" from her eponymous debut album.  The album produced four chart-topping singles in the US and began what would become a string of commercially successful albums which solidified the singer as Columbia Records' highest selling act.  Carey and Boyz II Men spent a record sixteen weeks atop the "Billboard" Hot 100 in 1995–1996 with "One Sweet Day," which remains the longest-running number-one song in US chart history.  Following a contentious divorce from Sony Music head Tommy Mottola, Carey adopted a new image and traversed towards hip hop with the release of "Butterfly" (1997).  In 1998, she was honored as the world's best-selling recording artist of the 1990s at the World Music Awards and subsequently named the best-selling female artist of the millennium in 2000.
Answer: Mariah Carey