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
The lens contains the oldest cells in – 
Select and explain. 
A. Nucleus, B. Anterior surface of lens, C. Posterior surface of lens, D. Nucleo–cortical junction
A: Nucleus
Answer: A: Nucleus 
Explanation: The nucleus is the central part containing older fibres. Embryonic zone of the nucleus (embryonic nucleus) contains oldest fibres.
The cortex contains the youngest fibres.