Question: when did the battle of lexington and concord happen
[{'answer': 'April 19 , 1775', 'provenance': [{'wikipedia_id': '4321886', 'title': 'Battles of Lexington and Concord', 'start_paragraph_id': 36, 'start_character': 180, 'end_paragraph_id': 36, 'end_character': 195, 'bleu_score': 1.0, 'section': 'Section::::The Battles.:Lexington.\n'}]}, {'provenance': [{'wikipedia_id': '4321886', 'title': 'Battles of Lexington and Concord', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 416, 'bleu_score': 0.9684940092844061, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15923803042350290573}, 'section': 'Section::::Abstract.'}]}]