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: Physiology
[{'content': 'Thrombopoietin is produced by \nSelect and explain. \nA. Monocytes, B. Liver, C. Megakaryocyte, D. Megakaryoblast', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]