The half potential of $Cl^{-1}(C_1)/AgCl/Ag$ electrode.Given the value of $E^0$ for $Ag^++e^-\rightarrow Ag$ and $K_{sp}$ of AgCl is
$\begin{array}{1 1}(a)\;E^0_{Ag^+/Ag}-0.059\log \large\frac{C_1}{K_{sp}^2}\\(b)\;E^0_{Ag^+/Ag}-0.059\log \large\frac{C_1^2}{K_{sp}^2}\\(c)\;E^0_{Ag^+/Ag}-0.059\log \large\frac{C_1}{K_{sp}}\\(d)\;E^0_{Ag^+/Ag}-0.059\log \large\frac{C_1}{K_{sp}}\end{array}$