Pure Benzene freezes at 5.4 °C. A solution of0.223 g of phenyl acetic acid $\left({\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{CH}}_2\mathrm{COOH}\right)$ in 4.4 g of benzene $\left(K_{\mathrm{f}}=5.12 \mathrm{K} \mathrm{kg}{ \mathrm{mol}}^{-1}\right)$ freezes at 4.47 °C. From this observation, one can conclude that

phenyl acetic acid exists as such in benzene

phenyl acetic acid undergoes partial ionization in benzene

phenyl acetic acid undergoes complete ionization in benzene

phenyl acetic acid dimerizes in benzene.