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
Which of the following is not an open eruption technique for the exposure of impacted maxillary canine: 
Select and explain. 
A. Window technique, B. Full flap technique, C. Apically positioned flap, D. Tunnel approach
D: Tunnel approach
Answer: D: Tunnel approach 
Explanation: None