One coulomb of charge passes through solutions of ${\mathrm{AgNO}}_3 \mathrm{and} {\mathrm{CuSO}}_4$. The ratio of the amounts of silver and copper deposited on platinum electrodes used for electrolysis is

$$\begin{gathered} \frac{\mathrm{Mass} \mathrm{of} \mathrm{Ag} \mathrm{deposited}}{\mathrm{Mass} \mathrm{of} \mathrm{Cu} \mathrm{deposited}}=\frac{\mathrm{Eq}. \mathrm{mass} \mathrm{of} \mathrm{Silver} \left(\mathrm{Ag}\right)}{\mathrm{Eq}. \mathrm{mass} \mathrm{of} \mathrm{Copper} \left(\mathrm{Cu}\right)} \\ = \frac{{\displaystyle \raisebox{1ex}{$108$}\!\left/ \!\raisebox{-1ex}{$1$}\right.}}{{\displaystyle \raisebox{1ex}{$63.5$}\!\left/ \!\raisebox{-1ex}{$2$}\right.}}=\frac{108}{31.75} = 108:31.75 \end{gathered}$$

Therefore, the correct option is C