The strength of ligands discussed in spectrochemical series.
According to the limitations of VBT,
It does not give a quantitative interpretation of the thermodynamic or kinetic stabilities of coordination compounds.
Hybridisation of [Ni(CN)4]−2 is dsp2.
The outer electronic configuration of Ni2+ ion is 3d84s0.
It is a square planar complex. Cyanide ion is a strong field ligand, thus all electrons will be paired.
One 3d, one 4s and two 4porbitals undergo dsp2 hybridization, four equivalent dsp2 hybrid orbitals which are occupied by 4 electron pairs of 4 cyanide ligands.
This forms [Ni(CN)4]−2
cis−[PtCl2(en)2]2+ complex exhibits optical isomerism, hence, it has two isomers.
Hence statement B and C are correct.