Effective nuclear charge can be calculated by using the formula is    

Option -C  is the correct choice:  The effective nuclear charge is the net positive charge on the valence electrons which can be estimated by using equation${\mathrm{z}}^{*}=\mathrm{Z}-\mathrm{\sigma }$  , where   is the effective nuclear charge .${\mathrm{Z}}^{*}$ is the atomic number, $\mathrm{\sigma }$ is the number of shielding effect