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': 'Thickness of the adult crystalline lens is about: \nSelect and explain. \nA. 2.5 mm, B. 3.5 mm, C. 4.25 mm, D. 5 mm', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. 5 mm', 'role': 'assistant'}]