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 one of the following is used to bleach a discolored endodontically treated tooth? 
Select and explain. 
A. Ether, B. Chloroform, C. Superoxol, D. Sodium hypochlorite
C: Superoxol
Answer: C: Superoxol 
Explanation: None