The Mechanism for the Decomposition of Ozone in the Presence $\rarr$

The mechanism for the decomposition of ozone in the presence of a reactive chlorine atom is shown below.Which species functions as a catalyst?
O₃ + (UV light) $\rarr$ O + $\rarr$ ₂
Cl + O₃ $\rarr$ ClO + O₂
ClO + O $\rarr$ Cl + O₂

A) O
B) Cl
C) ClO
D) CFCl₃
E) O₂