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': 'Pericardial effusion is best diagnosed by: September 2004 \nSelect and explain. \nA. USG, B. Angiography, C. Gallium scan, D. Echocardiography', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. D i.e. Echocardiography', 'role': 'assistant'}]