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': 'Pulmonary embolism is best diagnosed by: \nSelect and explain. \nA. ECG, B. Perfusion scan, C. Angiography, D. Plain X-ray', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Angiography', 'role': 'assistant'}]