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
It is most difficult to perform apically positioned flap
procedure in: 
Select and explain. 
A. Facial surface of incisors, B. Lingual surface of incisors, C. Facial surface of third molars, D. Lingual surface of third molar
C: Facial surface of third molars
Answer: C: Facial surface of third molars 
Explanation: None