Question: who has won the most races at martinsville
[{'answer': 'Richard Petty', 'provenance': [{'wikipedia_id': '1719389', 'title': 'Martinsville Speedway', 'start_paragraph_id': 6, 'start_character': 166, 'end_paragraph_id': 6, 'end_character': 179, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}]