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
[{'content': 'The "in office" non vital bleaching technique is \nSelect and explain. \nA. Walking bleach, B. Power bleach technique, C. Thermo catalytic technique, D. Night guard technique', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]