Question: when did rock and roll start in britain
[{'answer': '1950s', 'provenance': [{'wikipedia_id': '23365906', 'title': 'British rock and roll', 'start_paragraph_id': 1, 'start_character': 146, 'end_paragraph_id': 1, 'end_character': 151, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '23365906', 'title': 'British rock and roll', 'start_paragraph_id': 4, 'start_character': 0, 'end_paragraph_id': 4, 'end_character': 764, 'bleu_score': 0.5485164942394041, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2920005169358947388}, 'section': 'Section::::Origins.\n'}]}]