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': "Bleeding time is prolonged in - \nSelect and explain. \nA. Von Willebrand's disease, B. Christmas disease, C. Haemophilia, D. Polycythemia", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]