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': 'Christmas disease is due to the deficiency of the following clotting factor: \nSelect and explain. \nA. Factor 8, B. Factor 9, C. Factor 11, D. Factor 12', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Haemophilia B or Christmas disease is due to the deﬁciency of factor 9.', 'role': 'assistant'}]