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': 'Causes of early onset of cataract are all except: \nSelect and explain. \nA. Diabetes mellitus, B. Smoking, C. Trauma, D. Recurrent episodes of diarrhoea', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Smoking', 'role': 'assistant'}]