This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thorax And Mediastinum, Subject name: Surgery
[{'content': 'Pneumothorax of what size generally needs operative treatment? \nSelect and explain. \nA. >10%, B. >20%, C. >30%, D. >40%', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Small pneumothoraxes (<20%) that are stable may be monitored if the patient has few symptoms Moderate (20%-40%) and large (>40%) pneumothoraxes nearly always are associated with persistent symptoms that cause physical limitations and require intervention.', 'role': 'assistant'}]