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': "Earliest sign of deep vein thrombosis is \nSelect and explain. \nA. Calf tenderness, B. Rise in temperature, C. Swelling of calf muscle, D. Homan's sign", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]