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
A 55 year old man who has been on bed rest for the past 10 days, complain of breathlessness and chest pain. The chest x-ray is normal. The next step in investigation should be: 
Select and explain. 
A. Lung ventilation - perfusion scan, B. Pulmonary aeriography, C. Pulmonary venous wedge angiography, D. Echocardiography
A: Lung ventilation - perfusion scan
Answer: A: Lung ventilation - perfusion scan 
Explanation: A i.e. Lung Ventilation Perfusion Scan The h/O breathlessness & chest pain after 10 days of bed rest points towards diagnosis of Pulmonary thromboembolism. So for diagnosing PTE the Vt screening investigation is Ventilation perfusion scanQ and the best/gold standard investigation is Pulmonary angiographyQ