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
According to the WHO classification of anterior teeth, 873.66 means: 
Select and explain. 
A. Crown and root fracture., B. Concussion or luxation., C. Intrusion or extrusion., D. Avulsion.
B: Concussion or luxation.
Answer: B: Concussion or luxation. 
Explanation: Andresen or WHO classification of anterior tooth fractures: