Identify correct statements:
(a) Hybridisation of Al in ${\left[\mathrm{Al}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{3+}$ is ${\mathrm{Sp}}^3\mathrm{d}$
(b) Boron is able to form  ${\mathrm{BF}}_6^{3-}$
$\left(\mathrm{c}\right)4{\mathrm{BF}}_3+3{\mathrm{LiAlH}}_4\to 2{\mathrm{B}}_2{\mathrm{H}}_6+3\mathrm{LiF}+3{\mathrm{AlF}}_3$
$\left(\mathrm{d}\right){\left[{\mathrm{SiCl}}_6\right]}^{2-}$ is known whereas ${\left[{\mathrm{SiF}}_6\right]}^{2-}$ not