According to the valence bond theory the hybridization of central metal atom is \( dsp^2 \) for which one of the following compounds?
\( \text{NiCl}_2 \cdot 6\text{H}_2\text{O} \)
\( \text{K}_2[\text{Ni}(\text{CN})_4] \)
\( \text{Na}_2[\text{NiCl}_4] \)
\( [\text{Ni}(\text{CO})_4] \)