Question: when did season 19 of big brother start
[{'answer': 'June 28 , 2017', 'provenance': [{'wikipedia_id': '51296550', 'title': 'Big Brother 19 (American season)', 'start_paragraph_id': 7, 'start_character': 73, 'end_paragraph_id': 7, 'end_character': 91, 'bleu_score': 1.0, 'section': 'Section::::Production.:Broadcasts.\n'}]}, {'provenance': [{'wikipedia_id': '51296550', 'title': 'Big Brother 19 (American season)', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 864, 'bleu_score': 0.986797956037998, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13371757701426724834}, 'section': 'Section::::Abstract.'}]}]