This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hematology, Subject name: Pharmacology
[{'content': 'A 40 year old man has megaloblastic anemia and early signs of neurological abnormality. The drug most probably required is: \nSelect and explain. \nA. Folic acid, B. Iron sulphate, C. Erythropoietin, D. Vitamin B12', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Deficiency of vitamin B12 results in megaloblastic anemia and demyelination. It can cause subacute combined degeneration of spinal cord and peripheral neuritis.', 'role': 'assistant'}]