In which of the following reactions, chlorine undergoes disproportionation?
\[
\begin{aligned}
\text{I.} \quad & \text{Reaction with cold, dilute NaOH} \\
\text{II.} \quad & \text{Reaction with hot, concentrated NaOH} \\
\text{III.} \quad & \text{Reaction with } \mathrm{H_2S}
\end{aligned}
\]
The correct answer is