Pick out the correct statement with respect to `[Mn(CN)_(6)]^(3-)`:
A. (a) It is `sp^3d^2` hybridised and tetrahedral
B. (b) It is `d^2sp^3` hybridised and octahedral
C. (c) It is `dsp^2` hybridised and square planar
D. (d) It is `sp^3d^2` hybridised and octahedral
