This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (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-cortical junction', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is \'a\' ie Nucleus Parson writes - "It is important to bear in mind that the central nucleus of the lens consists of the oldest cells and the periphery or cortex of the youngest."', 'role': 'assistant'}]