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': 'Best marker for iron deficiency is \nSelect and explain. \nA. Serum iron, B. Serum ferritin, C. Total iron binding capacity, D. Transferrin saturation', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ref Harrison 19 th ed pg 627-628 The serum ferritin level is a better indicator of iron overload than the marrow iron stain. However, in addition to storage iron, the marrow iron stain provides information about the effective delivery of iron to develop- ing erythroblasts.', 'role': 'assistant'}]