To solve this problem, we need to understand what a zwitterion is.$\newline$A zwitterion is a molecule that contains both positive and negative charges, but is overall electrically neutral.$\newline$Typically, zwitterions are formed by amino acids in aqueous solutions.$\newline$Let's analyze each option:$\newline$• Option 1: Benzoic acid is a carboxylic acid and does not form a zwitterion.$\newline$• Option 2: Acetanilide is an amide and does not form a zwitterion.$\newline$• Option 3: Aniline is an amine and does not form a zwitterion.$\newline$• Option 4: Glycine is an amino acid and can form a zwitterion.$\newline$In glycine, the amino group $(NH_2)$ can accept a proton to become $(NH_3^+),$ and the carboxyl group $(COOH)$ can lose a proton to become $(COO^-). \newline$Thus, glycine can exist as a zwitterion: $NH_3^+CH_2COO^-. \newline$Therefore, the correct option is Option 4.