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: Pathology
[{'content': 'Which of the following is Pan leukocyte marker \nSelect and explain. \nA. CD19, B. CD3, C. CD45, D. CD45 RO', 'role': 'user'}, {'content': 'Answer: C \nExplanation: CD 45 is Pan leukocyte marker.\nCD 45 RO is marker for MEMORY cell.', 'role': 'assistant'}]