This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Anatomy
[{'content': 'Which of the following surface protein is most often expressed in human hematopoietic stem cells? \nSelect and explain. \nA. CD22, B. CD45, C. CD15, D. CD34', 'role': 'user'}, {'content': 'Answer: D \nExplanation: .', 'role': 'assistant'}]