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: Surgery
[{'content': 'Brodie -Trendlenburg test demonstrates- \nSelect and explain. \nA. Mid - thigh perforation, B. Deep vein thrombosis, C. Sapheno - femoral incompetence, D. Calf perforators', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]