Question: when did bmw change body style 5 series
[{'answer': '1991', 'provenance': [{'wikipedia_id': '534396', 'title': 'BMW 5 Series', 'start_paragraph_id': 2, 'start_character': 126, 'end_paragraph_id': 2, 'end_character': 130, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': '2009', 'provenance': [{'wikipedia_id': '534396', 'title': 'BMW 5 Series', 'start_paragraph_id': 2, 'start_character': 197, 'end_paragraph_id': 2, 'end_character': 201, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '534396', 'title': 'BMW 5 Series', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 201, 'bleu_score': 0.7645630089166471, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2915798839219869815}, 'section': 'Section::::Abstract.'}]}]