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': "Jafferson's fracture is the fracture of - \nSelect and explain. \nA. Odontoid, B. C1, C. C2, D. C3", 'role': 'user'}, {'content': "Answer: B \nExplanation: Jafferson's fracture is the most common type offracture of atlas (1).", 'role': 'assistant'}]