This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Trauma, Subject name: Surgery
[{'content': 'Jefferson fracture is fracture of which spine \nSelect and explain. \nA. C1, B. C2, C. C3, D. C4', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Jefferson fracture is disruption of C1 ring in multiple locations; blow-out of ringHangman fracture is bilateral C2 pedicles with spondylolisthesisSabiston 20e pg: 443', 'role': 'assistant'}]