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
Non radiographic method of working length determination: 
Select and explain. 
A. Digital tactile sense, B. Apical periodontal sensitivity, C. Electronic apex locator, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: None