Step 1: {Intramolecular Hydrogen Bonding} In o-nitrophenol, the hydrogen atom of the \({O-H}\) group forms a hydrogen bond with the oxygen atom of the nitro group, resulting in a stable six-membered ring. In contrast, m-nitrophenol, p-nitrophenol, and phenol exhibit intermolecular hydrogen bonding. Therefore, option (A) is the correct choice.