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': 'In a middle aged male having back pain, syndesmophytes involving 4 continous veebrae are seen on Xray. The patient has ? \nSelect and explain. \nA. DISH, B. Ankylosing spondylitis, C. Rheumatoid ahritis, D. Osteoahritis', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Ankylosing spondylitis Back pain with syndesmatophytes in a middle aged man suggest the diagnosis of ankylosing spondylitis.", 'role': 'assistant'}]