This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: miscellaneous, Subject name: Pathology
[{'content': 'Periodic acid schiff stain shows Block positivity in - \nSelect and explain. \nA. Myeloblasts, B. Lymphoblasts, C. Monoblasts, D. Megakaryoblasts', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Lymphoblasts Myeloperoxidase: negative Sudan Black: negative Nonspecific esterase: negative PAS: block positivity Myeloblasts Myeloperoxidase: positive sudan black: positive nonspecific esterase: positive in M4 & M5 PAS: negative Ref: RAM DAS NAYAK 2nd Ed. Pg no:293', 'role': 'assistant'}]