Which of the following has a square planar geometry?
 

It is given to find out the compound which has a square planar geometry. 

The nature of the ligand affects the hybridization of the compound which in turn affects the geometry. 

Explanation

In ${\left[{\mathrm{PdCl}}_4\right]}^{2–}$, the oxidation state of Pt is +2. So, the electronic configuration is $5d^8$. 
Six electrons are paired and two remain unpaired in the ground state. 

${\mathrm{Cl}}^{-}$ is a weak ligand, yet it causes electron pairing in 5d, opening up one 5d orbital. This results in ${\mathrm{dsp}}^2$ hybridization and square planar geometry.

Hence the correct answer is C)${\left[{\mathrm{PdCl}}_4\right]}^{2–}$