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
Pneumothorax of what size generally needs operative treatment? 
Select and explain. 
A. >10%, B. >20%, C. >30%, D. >40%
B: >20%
Answer: B: >20% 
Explanation: 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.