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
Extent of severity index, the examination 
Select and explain. 
A. Involves all teeth, B. Only six teeth, C. Is done with naber's probe, D. None of the above
A: Involves all teeth
Answer: A: Involves all teeth 
Explanation: None