Question: who has the best home run to at bat ratio
[{'answer': 'Mark McGwire', 'provenance': [{'wikipedia_id': '7011158', 'title': 'At bats per home run', 'start_paragraph_id': 1, 'start_character': 197, 'end_paragraph_id': 1, 'end_character': 209, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '7011158', 'title': 'At bats per home run', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 540, 'bleu_score': 0.9806740509884301, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2621415955533603910}, 'section': 'Section::::Abstract.'}]}]