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 substances play a major role in regulating cell-cell and cell-matrix interaction in cementum? 
Select and explain. 
A. Sharpey's fibers, B. Intrinsic fibers, C. Proteoglycans, D. Phosphoproteins
C: Proteoglycans
Answer: C: Proteoglycans 
Explanation: None