Question: number of vehicles registered in the united states
[{'answer': '263.6 million', 'provenance': [{'wikipedia_id': '5470103', 'title': 'Passenger vehicles in the United States', 'start_paragraph_id': 2, 'start_character': 163, 'end_paragraph_id': 2, 'end_character': 176, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]