This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lens, Subject name: Ophthalmology
[{'content': 'Lens contains the oldest cells in- \nSelect and explain. \nA. Nucleus, B. Anterior surface of lens, C. Posterior surface of lens, D. Nucleo- coical junction', 'role': 'user'}, {'content': "Answer: A \nExplanation: Nucleus is the central pa containing older fibres. Embryonic zone of nucleus (embryonic nucleus) contains oldest fibres. Coex contains the youngest fibres. Ref: Parson's 22nd/e p.261&21st/e p.256,257; Khurana 7th/e p.185&4th/e p.167.", 'role': 'assistant'}]