Question: who is the only professional boxer to end his career undefeated with a record of 49-0
[{'answer': 'Rocco Francis Marchegiano', 'provenance': [{'wikipedia_id': '154971', 'title': 'Rocky Marciano', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 25, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '154971', 'title': 'Rocky Marciano', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 423, 'bleu_score': 0.718797235055585, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5948632121469704435}, 'section': 'Section::::Abstract.'}]}]