Question: what is the political party system of the united states
[{'answer': 'two - party system', 'provenance': [{'wikipedia_id': '249433', 'title': 'Political parties in the United States', 'start_paragraph_id': 31, 'start_character': 51, 'end_paragraph_id': 31, 'end_character': 77, 'bleu_score': 1.0, 'section': 'Section::::Modern U.S. political party system.\n'}]}]