This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Ophthalmology
[{'content': 'Most common cause of rubeosis iridis is \nSelect and explain. \nA. Vitreous hemorrhage, B. CRVO, C. CRAO, D. Diabetes mellitus', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Rubeosis iridis is a condition in which new blood vessels form on the anterior surface of the iris. It occurs in diabetics of long standing and in thrombosis of the retinal vein.', 'role': 'assistant'}]