Which of the following is an example of an ionic compound?

Sodium chloride ($\text{NaCl}$) is an ionic compound formed by the complete transfer of electrons from a sodium atom ($\text{Na}$) to a chlorine atom ($\text{Cl}$), resulting in ${\text{Na}}^{+}$ and ${\text{Cl}}^{-}$ ions bound together by strong electrostatic forces. ${\text{H}}_2\text{O}$, ${\text{CH}}_4$, and ${\text{CO}}_2$ are covalent compounds.