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': 'Crescent fracture is \nSelect and explain. \nA. Fracture of iliac crest, B. Fracture of coccyx, C. Fracture of calcaneum, D. Fracture of Atlas', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]