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
Pure histological landmark for termination of cleaning, shaping and obturation is 
Select and explain. 
A. CDJ, B. Apical foramen, C. Apical constriction, D. All of the above
A: CDJ
Answer: A: CDJ 
Explanation: None