Identify the compound that exhibits tautomerism.

Tautomerism (Keto-enol) occurs in compounds having an $\alpha$ -hydrogen atom adjacent to a carbonyl group ($>C=O$). $2$ -Pentanone (${\text{CH}}_3{\text{COCH}}_2{\text{CH}}_2{\text{CH}}_3$) has $\alpha$ -hydrogens and can exist in enol form.Note: Phenol also exists in keto-enol equilibrium but the enol is highly stable.