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 the principle fibre group of the periodontal ligament 
Select and explain. 
A. Horizontal, B. Oblique, C. Alveolar crest, D. Transseptal
D: Transseptal
Answer: D: Transseptal 
Explanation: None