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
Primary function of cementum is 
Select and explain. 
A. Root formation, B. Attachment, C. Repair, D. Protection
B: Attachment
Answer: B: Attachment 
Explanation: The primary function of cementum is to provide attachment of the tooth to alveolar bone socket through Sharpey’s fibres.