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
Periodic acid schiff stain shows Block positivity in - 
Select and explain. 
A. Myeloblasts, B. Lymphoblasts, C. Monoblasts, D. Megakaryoblasts
B: Lymphoblasts
Answer: B: Lymphoblasts 
Explanation: 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