A. calcium phosphate
A.
B. calcium carbonate
B.
C. calcium oxide
C.
D. potassium
D.
Correct Answer: B
সঠিক উত্তর: B
Explanation
ব্যাখ্যা
Tooth enamel is primarily composed of calcium phosphate, arranged in a crystal structure called hydroxyapatite. This mineral, along with other calcium-based compounds, gives enamel its hardness and durability, making it the hardest substance in the human body.