Question: when did lift every voice and sing became black national anthem
[{'answer': '1919', 'provenance': [{'wikipedia_id': '341011', 'title': 'Lift Every Voice and Sing', 'start_paragraph_id': 4, 'start_character': 30, 'end_paragraph_id': 4, 'end_character': 34, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}]