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: Pathology
[{'content': 'Most common factor in development of diabetic nephropathy is - \nSelect and explain. \nA. Previous kidney disease, B. Associated hypertension, C. Duration of diabetes, D. Control with treatment', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]