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
Spontaneous pneumothorax exceeding ……………. % of chest cavity should have a chest tube inserted - 
Select and explain. 
A. 10, B. 25, C. 45, D. 60
B: 25
Answer: B: 25 
Explanation: Exact answer according to Schwartz in 30%.