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': "A 17 year old boy presented with total count of 138 x 109 /L with 80% blasts on the peripheral smear. Chest X-ray demonstrated a large mediastinal mass. Immunophenotyping of this patient's blasts would most likely demonstrate: \nSelect and explain. \nA. No surface antigens (null phenotype), B. An immature T cell phenotype (Tdt/D34/CD7 positive), C. Myeloid markers, such as CD13, CD33 and CD15, D. B cell markers, such as CD19, CD20 and CD22", 'role': 'user'}, {'content': 'Answer: B \nExplanation: . An immature I$? cell phenotype (Tdt/D34/CD7 positive)', 'role': 'assistant'}]