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: Orthopaedics
[{'content': 'Unna boot is used in treatment of \nSelect and explain. \nA. Fracture of ankle joint, B. Calcaneum fracture, C. Varicose ulcer, D. Diabetic foot ulcer', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]