Question: when was the star spangled banner declared the national anthem
[{'answer': 'March 4 , 1931', 'provenance': [{'wikipedia_id': '31064', 'title': 'The Star-Spangled Banner', 'start_paragraph_id': 25, 'start_character': 701, 'end_paragraph_id': 25, 'end_character': 715, 'bleu_score': 1.0, 'section': 'Section::::Early history.:National anthem.\n'}]}]