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: Dental
[{'content': 'According to the WHO classification of anterior teeth, 873.66 means: \nSelect and explain. \nA. Crown and root fracture., B. Concussion or luxation., C. Intrusion or extrusion., D. Avulsion.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Andresen or WHO classification of anterior tooth fractures:', 'role': 'assistant'}]