Question: what is the standard and poor's 500 index
[{'answer': 'stock market index', 'provenance': [{'wikipedia_id': '170992', 'title': 'S&P 500 Index', 'start_paragraph_id': 1, 'start_character': 45, 'end_paragraph_id': 1, 'end_character': 63, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]