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: Medicine
[{'content': 'Most common cause of myelophthisic anaemia - \nSelect and explain. \nA. Multiple myeloma, B. NHL, C. Leukaemia, D. Multiple secondaries', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]