Pick out the correct statement with respect to $\require{mhchem}\ce{[Mn(CN)6]^3-}$.
(a) It is $sp^3d^2$ hybridised and tetrahedral.
(b) It is $d^2sp^3$ hybridised and octahedral.
(c) It is $dsp^2$ hybridised and square planar.
(d) It is $sp^3d^2$ hybridised and octahedral.
(a) It is $sp^3d^2$ hybridised and tetrahedral.
(b) It is $d^2sp^3$ hybridised and octahedral.
(c) It is $dsp^2$ hybridised and square planar.
(d) It is $sp^3d^2$ hybridised and octahedral.