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: Orthopaedics
[{'content': "Not an indication for surgery in Pott's spine \nSelect and explain. \nA. No improvement clinically after 4 weeks of ATT, B. Stage 3 disease, C. Bowel and bladder involvement, D. Stage 4 disease", 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]