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
Time of application for cold pulp testing: 
Select and explain. 
A. 5 second, B. 10 second, C. 15 second, D. 20 second.
C: 15 second
Answer: C: 15 second 
Explanation: None