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 type of cataract is: \nSelect and explain. \nA. Blue dot, B. Zonular, C. Cupuliform, D. Cuneiform', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. Blue dot', 'role': 'assistant'}]