Which one of the following molecules contains no $\pi$ bond?

Shutterstock Explore ${\text{CO}}_2$: $O=C=O$ (Two $\pi$ bonds).${\text{SO}}_2$: Contains $S=O$ bonds (One or more $\pi$ bonds depending on resonance).${\text{NO}}_2$: Contains a double bond (One $\pi$ bond).${\text{H}}_2\text{O}$: Oxygen is $s{p}^3$ hybridized and forms two single ($\sigma$) bonds with Hydrogen. There are no multiple bonds, hence no $\pi$ bonds.