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
Three-wall defects most frequently occur: 
Select and explain. 
A. On the lingual aspect, B. On the facial aspect, C. In the furcation, D. In the interdental area
D: In the interdental area
Answer: D: In the interdental area 
Explanation: None