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: Ophthalmology
[{'content': 'Diabetic retinopathy is related to: \nSelect and explain. \nA. Duration of disease, B. Severity of disease, C. Family history, D. Control of diabetes', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Duration of disease', 'role': 'assistant'}]