In trivalent state most of the 13th group compounds being covalent are hydrolysed in water. Trichlorides of group 13 on hydrolysis in water form tetrahedral [M(OH)4]− species, the hybridisation state of element M is sp3.
In case of aluminium, acidified aqueous solution forms octahedral [Al(H2O)6]3+ ion, which has an aluminium as a central metal atom and water molecules as ligands. The aluminium is in +3 oxidation state and forms6sp3d2 hybrid orbitals.
Hence option D is the answer.