This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System, Subject name: Radiology
[{'content': 'Diagnosis is: \nSelect and explain. \nA. Right pneumothorax, B. Left pneumothorax, C. Right hydropneumothorax, D. Left hydropneumothorax', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C Right hydropneumothoraxCXR shows lucent (black) lateral aspect of right hemithorax with air fluid level in it-s/o hydropneumothorax. An expiratory CXR better than an inspiratory CXR for a diagnosis of pneumothorax. CT Thorax is IOC for pneumo/hydro- pneumothorax.', 'role': 'assistant'}]