Question: who sings the rap in baby by justin bieber
[{'answer': 'Ludacris', 'provenance': [{'wikipedia_id': '25788953', 'title': 'Baby (Justin Bieber song)', 'start_paragraph_id': 1, 'start_character': 362, 'end_paragraph_id': 1, 'end_character': 370, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '25788953', 'title': 'Baby (Justin Bieber song)', 'start_paragraph_id': 9, 'start_character': 0, 'end_paragraph_id': 9, 'end_character': 1173, 'bleu_score': 0.944861858049253, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15747556340991719449}, 'section': 'Section::::Style and composition.\n'}]}, {'provenance': [{'wikipedia_id': '25788953', 'title': 'Baby (Justin Bieber song)', 'section': 'Section::::Abstract.', 'start_paragraph_id': 1, 'end_paragraph_id': 1, 'meta': {'evidence_span': ['"Baby" is a song by Canadian recording artist Justin Bieber. It was released as the lead single from the latter half of Bieber\'s debut album, "My World 2.0". The track was written by Bieber with Christopher "Tricky" Stewart and Terius "The-Dream" Nash, both of whom worked with Bieber on "One Time", and also by R&B singer Christina Milian and labelmate, rapper Ludacris.\rhighlight sentence(s) containing evidence, not only the answer', '"Baby" is a song by Canadian recording artist Justin Bieber. It was released as the lead single from the latter half of Bieber\'s debut album, "My World 2.0". The track was written by Bieber with Christopher "Tricky" Stewart and Terius "The-Dream" Nash, both of whom worked with Bieber on "One Time", and also by R&B singer Christina Milian and labelmate, rapper Ludacris.']}}]}, {'provenance': [{'wikipedia_id': '35598237', 'title': 'All Around the World (Justin Bieber song)', 'section': 'Section::::Abstract.', 'start_paragraph_id': 1, 'end_paragraph_id': 1, 'meta': {'evidence_span': ['"All Around the World" is a song by Canadian singer Justin Bieber, from his third studio album, "Believe" (2012). It was written by Bieber, Sir Nolan and Nasri of The Messengers in collaboration with Ludacris, who guest features. This was the second collaboration between Bieber and Ludacris, having previously collaborated on "Baby" (2010). It was first released on June 4, 2012, as a promotional single from the album. The song was released as the fourth international single, and the fifth and final US single on February 26, 2013. The Eurodance track features a similar instrumentation to songs by Britney Spears, Chris Brown and Usher. Lyrically, it features Bieber singing to his love interest that "all around the world, people want to be loved". "All Around the World" received mostly positive reviews from music critics, who welcomed the song\'s Eurodance style. The song had moderate success worldwide, reaching the top ten in several countries, such as Belgium, Canada and Norway. Bieber promoted the song through live performances and a music video.', 'sengers in collaboration with Ludacris, who guest features. This was the second collaboration between Bieber and Ludacris, having previously collaborated on "Baby" (2010)']}}]}, {'provenance': [{'wikipedia_id': '25788953', 'title': 'Baby (Justin Bieber song)', 'section': 'Section::::Critical reception.\n', 'start_paragraph_id': 12, 'end_paragraph_id': 12, 'meta': {'evidence_span': ['The midtempo number\'s undeniably contagious chorus should keep Bieber\'s tween fan base satisfied, and Ludacris\' brief cameo adds a welcome urban twist." Bertoli went on to say, "The matchup adds a layer of maturity to Bieber\'s repertoire and should further solidify his growing presence on the charts."', 'Nick Levine of Digital Spy felt the song was "no great departure from what he\'s given us before", but felt the production of Tricky and The-Dream helped give the song a "simple", "big" chorus about "puppy love" that works. Melanie Bertoldi of "Billboard" said, "The midtempo number\'s undeniably contagious chorus should keep Bieber\'s tween fan base satisfied, and Ludacris\' brief cameo adds a welcome urban twist." Bertoli went on to say, "The matchup adds a layer of maturity to Bieber\'s repertoire and should further solidify his growing presence on the charts." "Rap-Up" magazine said that "the sweet pop fare gets a little street cred courtesy of the teen sensation\'s labelmate Ludacris." Jody Rosen of "Rolling Stone" appreciated the song\'s vintage doo-wop and fifties aesthetic and hip-hop chants, and said the song included "one of the catchiest choruses concocted by the-Dream and Tricky Stewart, the duo behind "Umbrella" and "Single Ladies." Luke O\'Neill of "Boston Globe" had mixed thoughts about the song calling Ludacris\' cameo "goofy", and said, the song "effects a musical anachronism, albeit a catchy one, but in this sped-up recycling moment all styles all at once are grist for the mill."']}}]}]