Question: when did the star spangled banner became a national anthem
[{'answer': 'March 3 , 1931', 'provenance': [{'wikipedia_id': '31064', 'title': 'The Star-Spangled Banner', 'start_paragraph_id': 25, 'start_character': 642, 'end_paragraph_id': 25, 'end_character': 656, 'bleu_score': 1.0, 'section': 'Section::::Early history.:National anthem.\n'}]}, {'provenance': [{'wikipedia_id': '31064', 'title': 'The Star-Spangled Banner', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 295, 'bleu_score': 0.8615894073865311, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5507541378052294866}, 'section': 'Section::::Abstract.'}]}]