This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cornea, Subject name: Ophthalmology
[{'content': 'Normal corneal endothelial count in a young adult is \nSelect and explain. \nA. 500/mm2, B. 2500/mm2, C. 4500/mm2, D. 6500/mm2', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. (b) 2500/mm2Ref Parson's 21/e, p. 120* The cell density of endothelium is around 2800cells/mm2(2400-3000cells/mm2) in young adults, which decreases with the advancing age.", 'role': 'assistant'}]