Question: when did the united states became a sovereign nation
[{'answer': 'July 4 , 1776', 'provenance': [{'wikipedia_id': '31874', 'title': 'United States Declaration of Independence', 'start_paragraph_id': 64, 'start_character': 76, 'end_paragraph_id': 64, 'end_character': 89, 'bleu_score': 1.0, 'section': 'Section::::History of the documents.\n'}]}]