This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lung, Subject name: Surgery
[{'content': 'In case of pneumothorax - \nSelect and explain. \nA. Cavity in lung, B. Air fills in pleural space, C. Pus fills in pleural space, D. Blood in pleural space', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Air fills in pleural space * Pneumothorax- Air in pleural cavity* Empyema- Pus in pleural cavity* Hemothorax- Blood in pleural space* Hydrothorax- Fluid in pleural cavity", 'role': 'assistant'}]