The correct answer is Enamel.

- Among the various tissues in the human body, enamel exhibits the highest degree of mineralization and hardness.
- Enamel is composed of approximately 96% mineral content, primarily hydroxyapatite crystals, which give it its exceptional hardness and durability.
- This high mineral content makes enamel the hardest substance in the human body, essential for protecting teeth from mechanical forces and chemical erosion.

In comparison:
- Dentin has a mineral content of roughly 70% and is less hard than enamel, serving as a supportive and resilient structure beneath the enamel.
- Cementum covers the tooth root and has a mineral content of around 45-50%, making it softer than both enamel and dentin.
- Alveolar bone supports the teeth in the jaw and contains approximately 65% mineral content, which is less mineralized than enamel.

Reference: Orban's Oral Histology, 15th Edition, Chapter 3 - Enamel and Dentin, Page 47