Question: when did the iphone 7 go on sale
[{'answer': 'September 16 , 2016', 'provenance': [{'wikipedia_id': '51539250', 'title': 'IPhone 7', 'start_paragraph_id': 1, 'start_character': 271, 'end_paragraph_id': 1, 'end_character': 290, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '51539250', 'title': 'IPhone 7', 'start_paragraph_id': 1, 'start_character': 9, 'end_paragraph_id': 1, 'end_character': 620, 'bleu_score': 0.8544806866029301, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7172961479263037107}, 'section': 'Section::::Abstract.'}]}]