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
[{'content': 'In which condition breath sounds are absent: \nSelect and explain. \nA. Bronchial asthma, B. Pneumothorax, C. Emphysema, D. Pneumonia', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]