This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Chronic Myelogenous Leukemia, Subject name: Pathology
[{'content': 'In chronic myeloid leukemia CML, serum vitamin B12 level is: \nSelect and explain. \nA. Slightly decreased, B. Normal, C. Markedly decreased, D. Increased', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Biochemical abnormalities in CML include a low leukocyte alkaline phosphatase score and high levels of vitamin B12, uric acid, lactic dehydrogenase, and lysozyme.', 'role': 'assistant'}]