Which of the following ions in solution undergoes disproportionation?

Solution undergoes disproportionation is Cuprous ion.

Cuprous ion can generate both lower and greater oxidation products. Cuprous ion can undergo disproportionation

$\begin{array}{cc}{\mathrm{Cu}}^{+}\to \mathrm{Cu}+{\mathrm{Cu}}^{+2}& \end{array}$

+1             0      +2

Hence, option C is correct.