This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vascular surgery, Subject name: Surgery
[{'content': 'Investigation of choice for DVT is \nSelect and explain. \nA. Duplex USG, B. VQ scan, C. Plethysmography, D. D-dimer assay', 'role': 'user'}, {'content': "Answer: A \nExplanation: . Duplex scanning shows noncompressible vein which is wider than normal.On compression over calf muscles,it does not show any augmentation of flow.Normal venous sound atg the area of femoral vein which disappears during inspiration is conspicuously absent in DVT. Refer page no 224 of SRB's manual of surgery 5 th edition.", 'role': 'assistant'}]