Question: who is the most decorated us olympian of all time
[{'answer': 'American swimmer Michael Phelps', 'provenance': [{'wikipedia_id': '18855244', 'title': 'List of multiple Olympic medalists', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 31, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]