Correct Answer - C
Here nickel is in `+2` oxidation state has the electronnc configuration `3d^(8)` . Since `CN^(-)` ion is a strong field lignd, the electronic configuration is reshuffled to pair up all the electrons so as to provide one empty orbital for `dsp^(2)` hybrization.
`[Ni(CN)_(4)]^(2-)`
Four pairs of form `4CN^(-)` ligands electrons
Each of the hybridised orbitals receives a pair of electrons form a cyanide ion.