Multiple choice

Which of the following is the hardest substance in the body?

  1. Hair

  2. Bone

  3. Nail

  4. Enamel

  5. Brain

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Tooth enamel is the hardest substance in the human body, composed primarily of hydroxyapatite crystals. It measures 5 on the Mohs scale of mineral hardness, harder than bone (which is around 3-4). Enamel protects teeth from wear and decay.