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: Medicine
In which condition breath sounds are absent: 
Select and explain. 
A. Bronchial asthma, B. Pneumothorax, C. Emphysema, D. Pneumonia
B: Pneumothorax
Answer: B: Pneumothorax 
Explanation: None