Question: who has the most aircraft carriers in the world
[{'answer': 'United States', 'provenance': [{'wikipedia_id': '60982', 'title': 'List of aircraft carriers', 'start_paragraph_id': 237, 'start_character': 11, 'end_paragraph_id': 237, 'end_character': 24, 'bleu_score': 1.0, 'section': 'Section::::List of countries that have operated aircraft carriers.:United Kingdom.\n'}]}]