Question: when was the iphone first introduced to the market
[{'answer': 'June 29 , 2007', 'provenance': [{'wikipedia_id': '13678080', 'title': 'History of iPhone', 'start_paragraph_id': 27, 'start_character': 359, 'end_paragraph_id': 27, 'end_character': 379, 'bleu_score': 1.0, 'section': 'Section::::United States release.:Price drop outcry.\n'}]}, {'provenance': [{'wikipedia_id': '13678080', 'title': 'History of iPhone', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 244, 'bleu_score': 0.8432101478853161, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15409260219061293190}, 'section': 'Section::::Abstract.'}]}]