Which of the following atoms is ${\mathrm{sp}}^2$ hybridized?

What is the hybridization of the nitrogen atom in the ammonium ion ${\mathrm{NH}}_4{+}^{\mathrm{}}$?

Given a carbon atom forming three $\sigma$ bonds and one $\pi$ bond, what type of hybrid orbitals are used by the carbon atom?

What is the hybridization of the oxygen atom in $C_2{H}_{6}O$ (dimethyl ether, ${\mathrm{CH}}_{3}O{\mathrm{CH}}_3$)?

In the molecule $C_2{H}_2$ (ethyne), how many carbon atoms are $\mathrm{sp}$ hybridized?

What is the hybridization of the carbon atom that is bonded to three hydrogens in acetic acid (${\mathrm{CH}}_3\mathrm{COOH}$)?

In the molecule $C_2{H}_4$ (ethene), what is the hybridization at each carbon atom?

What is the hybridization of the central atom in ${\mathrm{CO}}_2$?

In acetic acid, what is the hybridization of the carbon atom that is directly bonded to two oxygen atoms?