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 in the following cells: \nSelect and explain. \nA. Myeloblasts, B. Lymphoblasts, C. Monoblasts, D. Megakaryoblasts', 'role': 'user'}, {'content': "Answer: B \nExplanation: In acute lymphocytic leukemia (ALL), cells show a varied staining pattern with periodic acid schiff (PAS) stain. Lymphoblasts of ALL may show a coarse block pattern of activity, a finely diffuse pattern, or a combinations of the two patterns, or they may be negative. Cells from Burkitt's lymphoma are generally negative. Ref: Hematology: clinical principles and applications, 2007, Page 401.", 'role': 'assistant'}]