Question: who has the nfl record for most rushing yards in a career
[{'answer': 'Emmitt Smith', 'provenance': [{'wikipedia_id': '8571883', 'title': 'List of National Football League career rushing yards leaders', 'start_paragraph_id': 1, 'start_character': 168, 'end_paragraph_id': 1, 'end_character': 180, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]