Question: who sang ava gardner's part in showboat
[{'answer': 'Annette Warren', 'provenance': [{'wikipedia_id': '16885650', 'title': 'Show Boat (1951 film)', 'start_paragraph_id': 28, 'start_character': 1292, 'end_paragraph_id': 28, 'end_character': 1306, 'bleu_score': 1.0, 'section': 'Section::::Adaptation.\n'}]}, {'provenance': [{'wikipedia_id': '16885650', 'title': 'Show Boat (1951 film)', 'start_paragraph_id': 41, 'start_character': 0, 'end_paragraph_id': 41, 'end_character': 80, 'bleu_score': 0.8242367502646051, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1791490302071453279}, 'section': 'Section::::Cast.\n'}]}]