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: Unknown
[{'content': 'The operative procedure known as “micro fracture” is done for the \nSelect and explain. \nA. Delayed union of femur, B. Nonunion of tibia, C. Loose bodies of ankle joint, D. Osteochondral defect of femur', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Microfracture is an orthopedic procedure used to treat osteochondral defects (damaged areas of articular cartilage of\nthe knee).', 'role': 'assistant'}]