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': 'Commonest congenital cataract is: \nSelect and explain. \nA. Nuclear, B. Zonular, C. Capsular, D. Coralliform', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Zonular', 'role': 'assistant'}]