The correct statement among the followring is:

We analyze the magnetic properties of three nickel complexes.

1. $$Ni(CO)_4$$:

Nickel is in the 0 oxidation state with configuration $$[Ar]\,3d^{10}$$. CO is a strong field ligand. With all 10 d-electrons paired, this complex is diamagnetic. The geometry is tetrahedral (sp$$^3$$ hybridization).

2. $$[NiCl_4]^{2-}$$:

Nickel is in the +2 oxidation state with configuration $$[Ar]\,3d^8$$ (2 unpaired electrons). Cl$$^-$$ is a weak field ligand, so no electron pairing occurs. The complex adopts a tetrahedral geometry (sp$$^3$$) with 2 unpaired electrons. This complex is paramagnetic.

3. $$[Ni(CN)_4]^{2-}$$:

Nickel is in the +2 oxidation state with configuration $$[Ar]\,3d^8$$. CN$$^-$$ is a strong field ligand, causing electron pairing. The complex adopts a square planar geometry (dsp$$^2$$ hybridization) with all electrons paired. This complex is diamagnetic.

Summary:

$$Ni(CO)_4$$: diamagnetic, $$[Ni(CN)_4]^{2-}$$: diamagnetic, $$[NiCl_4]^{2-}$$: paramagnetic.

Option B states: "$$Ni(CO)_4$$ and $$[Ni(CN)_4]^{2-}$$ are diamagnetic and $$[NiCl_4]^{2-}$$ is paramagnetic." (The option text contains a typographical error showing $$[NiCl_4]^{2-}$$ where it should say $$[Ni(CN)_4]^{2-}$$, but the intended meaning matches our analysis.)

The correct answer is Option B.