(b) Ideal solutions are the solutions which obey Raoult's law at all temperatures and pressures. The interactions of solute-solute, solvent-solvent and solute-solvent in these solutions are almost similar. No association/dissociation occurs in these solutions. Mixture of phenol and aniline shows negative deviation from ideal behaviour and forms an azeotropic mixture. The phenol-aniline interactions are stronger than phenol-phenol or aniline-aniline interactions. ‌∆V‌mixing ‌<0 ‌∆H‌mixing ‌>0 Hence, it does not form an ideal solution. Rest options (I), (II) and (III) form ideal solution.