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: Surgery
[{'content': 'Which of the following conditions can cause bony ankylosis? \nSelect and explain. \nA. Rheumatoid ahritis, B. Pyogenic ahritis, C. Osteo ahritis, D. Traumatic ahritis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Pyogenic ahritis causes bony ankylosis.', 'role': 'assistant'}]