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
Odontoclasts for tooth resorption are mainly derived from: 
Select and explain. 
A. PDL., B. Cementum., C. Bone., D. Dentin.
A: PDL.
Answer: A: PDL. 
Explanation: Odontoclasts for tooth resorption are mainly derived from PDL