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: Pathology
[{'content': 'Hemophilia B is due to: \nSelect and explain. \nA. Factor VII deficiency, B. Factor IX deficiency, C. Platelet deficiency, D. Vit C deficiency', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]