Question: when was the lake of the ozarks dam built
[{'answer': '1931', 'provenance': [{'wikipedia_id': '1546128', 'title': 'Bagnell Dam', 'start_paragraph_id': 7, 'start_character': 61, 'end_paragraph_id': 7, 'end_character': 65, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}]