Question: who was president when the hoover dam was built
[{'answer': 'Franklin D. Roosevelt', 'provenance': [{'wikipedia_id': '14308', 'title': 'Hoover Dam', 'start_paragraph_id': 1, 'start_character': 269, 'end_paragraph_id': 1, 'end_character': 290, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '14308', 'title': 'Hoover Dam', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 561, 'bleu_score': 0.8662162521492901, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 14581591329513676080}, 'section': 'Section::::Abstract.'}]}]