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': "All of the following are true about corneal endothelium except: \nSelect and explain. \nA. Cell density is about 3000 cells/min' at bih, B. Corneal decompensation occurs when cell count is decreased by 50 percent, C. Endothelial cells contain active pump mechanism, D. Endothelium is best examined by specular microscopy", 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Corneal decompensation occurs when cell count is decreased by 50 percent', 'role': 'assistant'}]