This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
[{'content': 'Lactic acid is produced in mouth by \nSelect and explain. \nA. Saccharolytic bacteria in supragingival region, B. Saccharolytic bacteria in subgingival region, C. Non-saccharolytic bacteria in supragingival region, D. Non-saccharolytic bacteria in subgingival region', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]