Substituents adjacent to the carboxyl group (\( \text{COOH} \)) of carboxylic acids, via their electron-withdrawing (-I) effect, influence acidity. These substituents withdraw electron density from the carboxylate ion, thereby stabilizing it and increasing acidity. Electronegativity order: \[F>Cl>Br>H.\]The most electronegative element, fluorine, exhibits the strongest -I effect, resulting in maximum carboxylate ion stabilization and highest acidity. Chlorine and bromine follow with progressively weaker withdrawing effects, while hydrogen has no such effect. Final Answer:\[\boxed{\text{FCH}_2\text{COOH}>\text{ClCH}_2\text{COOH}>\text{BrCH}_2\text{COOH}>\text{CH}_3\text{COOH}}\]