The d-orbital of the Cl atom does not include the free electron from the ${\mathrm{CO}}_3$ molecule. The d-orbital of the Cl atom does not include the free electron from the ${\mathrm{CO}}_3$  molecule. The center atom of ${\mathrm{Cl}}_2\mathrm{CO}$ is ${\mathrm{sp}}^2$ hybridized.

Thus, The free electron of ${\stackrel{°}{\mathrm{C}}\mathrm{lO}}_3$  is present in $d$-orbital of Cl-atom.

Hence, the option A is correct.