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': 'A 55-year-old man, who has been on bed rest for the past 10 days, complains of breathlessness and chest pain. The chest X-ray is normal. The next step in investigation should he: \nSelect and explain. \nA. I.ung ventilation - perfusion scan, B. Pulmonary aeriography, C. Pulmonary venous wedge angiography, D. Echocardiography', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. I.ung ventilation - perfusion scan', 'role': 'assistant'}]