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 diagnosed by: \nSelect and explain. \nA. USG, B. X-ray chest, C. Ventilation perfusion scan, D. CT scan', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. CT scan', 'role': 'assistant'}]