Question: who sang i wonder why he's the greatest dancer
[{'answer': 'American vocal group Sister Sledge', 'provenance': [{'wikipedia_id': '7152156', 'title': "He's the Greatest Dancer", 'start_paragraph_id': 1, 'start_character': 49, 'end_paragraph_id': 1, 'end_character': 83, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '7152156', 'title': "He's the Greatest Dancer", 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 343, 'bleu_score': 0.9250392488272071, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6195811266600679019}, 'section': 'Section::::Abstract.'}]}]