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
Incision of which fibres of PDL doesn't increase mobility of tooth: 
Select and explain. 
A. Oblique fibres, B. Alveolar crest fibres, C. Apical fibres, D. Transeptal fibres.
B: Alveolar crest fibres
Answer: B: Alveolar crest fibres 
Explanation: None