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
Which is the most likely to cause pulp necrosis? 
Select and explain. 
A. Subluxation, B. Extrusion, C. Avulsion, D. Concussion
C: Avulsion
Answer: C: Avulsion 
Explanation: To have pulp space infection, the pulp must first become necrotic. This will occur in a fairly serious injury in which displacement of the tooth results in severing of the apical blood vessels.