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
Dummer's classification is associated with: 
Select and explain. 
A. Apical constriction, B. Apical foramen, C. Root canal isthmus, D. No. of canals
A: Apical constriction
Answer: A: Apical constriction 
Explanation: Dummer’s classiﬁcation of topography of apical constriction: