Tooth enamel is the hardest substance found in the human body. What is it made up of - (1) Calcium carbonate (2) Limestone (3) Calcium phosphate (4) Calcium fluoride
(3) Calcium phosphate Explanation: The protective layer around your teeth, called enamel, is the strongest substance that our body produces. In fact, tooth enamel is stronger than any other substance on earth except for diamonds.