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: Radiology
[{'content': 'Increased radiolucency of one sided hemithorax may he caused by all the following except: \nSelect and explain. \nA. Obstructive emphysema, B. Pneumothorax, C. Expiratory film, D. Rotation', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Expiratory film', 'role': 'assistant'}]