In which of the following octahedral complexes of $\text{ Co(at. no. 27), }$ will the magnitude of ${\mathrm{\Delta }}_0$ be the highest ?

Since ${\mathrm{CN}}^{-}$ is the strongest ligand among those listed in the alternatives ${\left[\mathrm{Co}(\mathrm{CN}{)}_6\right]}^{3-}$ has the greatest  value for  ${\mathrm{\Delta }}_0$.

Hence correct option is D