Carboxylic acids are the most acidic compounds among the organic compounds. Due to presence of electron withdrawing group i.e. chlorine and fluorine, FCH2‌COOH and CH3CH2‌CHClCOOH are more acidic, than C6H5‌COOH and CH3‌COOH. Fluorine is more electron withdrawing group than chlorine. Therefore, FCH2‌COOH>CH3CH2‌CHClCOOH>C6H5‌COOH>CH3‌COOH