This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Radiology
[{'content': 'Interpret the following chest Xray \nSelect and explain. \nA. PDA, B. Pericardial effusion, C. Constrictive pericarditis, D. Emphysema', 'role': 'user'}, {'content': 'Answer: B \nExplanation: .', 'role': 'assistant'}]