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: Pharmacology
[{'content': 'All of the following are risk factors for increased lactic acidosis in patients on metformin therapy except \nSelect and explain. \nA. Advanced age, B. Liver dysfunction, C. Renal dysfunction, D. Smoking', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Metformin can result in lactic acidosis and the risk factors includes old age,renal and liver insufficiency, alcoholics.\nSmoking is not a risk factor.', 'role': 'assistant'}]