This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Chronic Venous Insufficiency, Subject name: Surgery
[{'content': 'Investigation of choice in DVT is - \nSelect and explain. \nA. Venogram, B. Colordoppler, C. Plethysmography, D. X-ray', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Color doppler", 'role': 'assistant'}]