Question: when did fluoridation of water begin in the u.s
[{'answer': 'January 25 , 1945', 'provenance': [{'wikipedia_id': '23817469', 'title': 'Water fluoridation in the United States', 'start_paragraph_id': 13, 'start_character': 339, 'end_paragraph_id': 13, 'end_character': 356, 'bleu_score': 1.0, 'section': 'Section::::History.:Early studies.\n'}]}, {'provenance': [{'wikipedia_id': '23817469', 'title': 'Water fluoridation in the United States', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 315, 'bleu_score': 0.962600167205617, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13600223874735579130}, 'section': 'Section::::Abstract.'}]}]