Question

nahco₃ is an example of —
a compound
an abbreviation
a mixture
an element

Explanation:

A compound is a substance made of two or more different elements chemically bonded together. $\text{NaHCO}_3$ (sodium bicarbonate) consists of sodium (Na), hydrogen (H), carbon (C), and oxygen (O) atoms chemically combined in a fixed ratio. An element is a single type of atom, a mixture is a physical combination of substances, and this is a chemical formula, not just an abbreviation.

Answer:

a compound