This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Haematology, Subject name: Anatomy
[{'content': 'In 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: Wintrobes hematology mentiins granulocytes contain and release B12 binding proteins.Markedly elevated transcobalamin 1 level are seen in chronic myelocytic leukemia and myeloid metaplasia whereas low levels are seen in chronic leucopenia and aplastic anemia. Williams hematology 8th adds that the increase is propoional to the total leucocyte count in untreated patients and falls with treatment.(ref Robbins 7th /697-698)', 'role': 'assistant'}]