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': 'Activation of which one of the following coagulation factor is not essential for haemostasis \nSelect and explain. \nA. XII, B. XI, C. IX, D. X', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]