The correct answer is Bone.

Among the hard tissues listed—enamel, dentin, cementum, and bone—only bone contains both blood vessels and nerve supply within its structure.

- Enamel is the hardest tissue in the body, but it is avascular (lacks blood vessels) and aneural (lacks nerve supply). It is composed primarily of mineral salts with no living cells, which is why it cannot repair itself once damaged.

- Dentin lies beneath enamel and contains microscopic tubules; however, it is avascular. Although it is sensitive due to the presence of odontoblastic processes within the tubules, it does not have its own direct blood supply or nerves.

- Cementum covers the root of the tooth and anchors it to the periodontal ligament. Like dentin, cementum is avascular and receives nutrients from the surrounding periodontal ligament, but does not contain blood vessels or nerves itself.

- Bone, on the other hand, is a living connective tissue that is richly supplied with blood vessels through Haversian and Volkmann’s canals, which provide essential nutrients and oxygen. It also contains a nerve supply that contributes to the sensation and regulation of bone metabolism.

Reference: Orban's Oral Histology, 14th Edition, Chapter 3: Hard Tissues, pp. 45-50