This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': 'Marker for B lymphocytes \nSelect and explain. \nA. CD34, B. CD33, C. CD19, D. CD20', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ref immunology by Roitt 6/e p 29; 30; 19 ;9/e p191 CD 19,20,22 are main markers of human B cells .othersB cell markers are CD72 and CD78', 'role': 'assistant'}]