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: Surgery
[{'content': 'Blast cells of ALL in childhood have: \nSelect and explain. \nA. Excessive mitochondria, B. Antibodies on WBC, C. CALLA+ve, D. Surface antigen', 'role': 'user'}, {'content': 'Answer: C \nExplanation: CALLA +ve The blast cells of ALL mayor may not react to Common Acute Lymphocytic Leukemia Antigen (CALLA). They are classified as CALLA +ve or CALLA -ve', 'role': 'assistant'}]