A chain started by a Cl atom propagates through the two steps $\mathrm{Cl}+\mathrm{O}{}_3\to \mathrm{ClO}+\mathrm{O}{}_2$ and $\mathrm{ClO}+\mathrm{O}\to \mathrm{Cl}+\mathrm{O}{}_2$. The chain ends when Cl reacts with methane, $\mathrm{Cl}+\mathrm{CH}{}_4\to \mathrm{HCl}+\mathrm{CH}{}_3$. Which statement about this termination is correct?

1. AIt regenerates Cl atoms from methane
2. BIt converts the active Cl atom into the inactive reservoir HCl, so the chain length is limited
3. CIt produces ozone from HCl
4. DIt makes the chain faster by producing ClO