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
Diabetic retinopathy is related to: 
Select and explain. 
A. Duration of disease, B. Severity of disease, C. Family history, D. Control of diabetes
A: Duration of disease
Answer: A: Duration of disease 
Explanation: Duration of disease