Question: when did cell phones become common in the us
[{'answer': 'the 1990s', 'provenance': [{'wikipedia_id': '1245539', 'title': 'History of mobile phones', 'start_paragraph_id': 55, 'start_character': 3, 'end_paragraph_id': 55, 'end_character': 12, 'bleu_score': 1.0, 'section': 'Section::::The early generations.:2G – Digital cellular.\n'}]}, {'provenance': [{'wikipedia_id': '1245539', 'title': 'History of mobile phones', 'start_paragraph_id': 55, 'start_character': 0, 'end_paragraph_id': 55, 'end_character': 466, 'bleu_score': 0.97451705556073, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5228180835811187833}, 'section': 'Section::::The early generations.:2G – Digital cellular.\n'}]}]