The correct answer is Cementum.

- Cementum is a specialized calcified connective tissue that covers the roots of teeth.
- Its primary function is to serve as the attachment site for the periodontal ligament fibers, which connect the tooth to the alveolar bone.
- This connection is essential for maintaining tooth stability within the dental socket and allows for slight tooth movement during mastication.
- Unlike enamel and dentin, which form the crown and body of the tooth respectively, cementum is unique in its role of linking the tooth to the surrounding alveolar bone.
- The alveolar bone proper forms the bony socket but does not directly attach to the tooth without the intermediary cementum and periodontal ligament.

Key points:
- Cementum covers the root surface of the tooth.
- It is responsible for anchoring the tooth by attaching to periodontal ligament fibers.
- These fibers connect the tooth to the alveolar bone, ensuring tooth stability.
- Enamel is the hard outer layer of the crown, and dentin forms the bulk of the tooth structure but does not attach to bone.
- The alveolar bone proper is the bone surrounding the roots but relies on cementum and periodontal ligaments for tooth attachment.

Reference: Ten Cate's Oral Histology, 9th Edition, Chapter 10: Periodontium / Page 220