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': 'The blast cells of acute lymphocytic leukemia in childhood contain \nSelect and explain. \nA. Surface antigen, B. CALLA Ag, C. Antibodies to WBC, D. Thrombocytopenia', 'role': 'user'}, {'content': 'Answer: B \nExplanation: CALLA (common acute lymptoblastic leukemia antigen) is CDIO\nCALLA positive acute leukemias have best progrosis.', 'role': 'assistant'}]