In the treatment of domestic water supplies, chlorine is introduced into the water so that $\text{HClO}$ is formed. $\text{Cl}_2(aq) + \text{H}_2\text{O}(l) \rightarrow \text{H}^+(aq) + \text{Cl}^-(aq) + \text{HClO}(aq)$. The $\text{HClO}$ then reacts further to produce $\text{ClO}^-$ ions. $\text{HClO}(aq) + \text{H}_2\text{O}(l) \rightleftharpoons \text{H}_3\text{O}^+(aq) + \text{ClO}^-(aq)$. Both $\text{HClO}$ and $\text{ClO}^-$ destroy bacteria by oxidation. By how much does the oxidation number of chlorine change when the $\text{ClO}^-$ ion is formed from aqueous chlorine?
- A$-1$
- B$0$
- C$+1$
- D$+2$