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': 'Periodic acid schiff stain shows Block positivity \nSelect and explain. \nA. Myeloblasts, B. Lymphoblasts, C. Monoblasts, D. Megakaryoblasts', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Lymphoblast contain cytoplasmic aggregates of periodic acid-schiff (PAS)-positive material.', 'role': 'assistant'}]