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 a pan T Cell marker \nSelect and explain. \nA. CD 2, B. CD 3, C. CD 19, D. CD 25', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]