Aluminium chloride exists as a dimer, Al2Cl6 in a solid state as well as in solution of non-polar solvents such as benzene. When dissolved in water, it gives:
The aluminium chloride reacts with the water rather than just dissolving in it. In the first instance, hexaaquaaluminium ions are formed together with chloride ions.
Al2Cl6+H2O→[A1(H2O)6]3++3C1−
Hence option B is correct.