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
The "in office" non vital bleaching technique is 
Select and explain. 
A. Walking bleach, B. Power bleach technique, C. Thermo catalytic technique, D. Night guard technique
C: Thermo catalytic technique
Answer: C: Thermo catalytic technique 
Explanation: None