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
Tooth movement is primarily a phenomenon involving: 
Select and explain. 
A. Pulp, B. Periodontal ligament, C. Dentin, D. Cementum
B: Periodontal ligament
Answer: B: Periodontal ligament 
Explanation: PDL ligament is primarily associated with orthodontic tooth movement.