Consider the following complex ions.

(P) ${\left[{\mathrm{CrCl}}_6\right]}^{3-}$ (Q) ${\left[\mathrm{Cr}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{3+}$

(R) ${\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_6\right]}^{3+}$ (S) ${\left[\mathrm{Cr}(\mathrm{CN}{)}_6\right]}^{3-}$

The correct order of ${\mathrm{\Delta }}_0$ is:

Since strength of ligand is directly proportional to ${\mathrm{\Delta }}_0$

correct order of ${\mathrm{\Delta }}_0$.

${\mathrm{CN}}^{-}>{\mathrm{NH}}_3>{\mathrm{H}}_2\mathrm{O}>{\mathrm{Cl}}^{-}$

Hence correct option is C