In stratosphere, which of the following elements acts as a catalyst in degradation of ozone and release of molecular oxygen?

Chlorofluorocarbons ($\text{CFCs}$) release chlorine atoms ($\text{Cl}$) when they are broken down by $\text{UV}$ rays in the stratosphere. Chlorine atoms react with ozone to form oxygen. The $\text{Cl}$ atoms are not consumed in the reaction; they act as catalysts, meaning one $\text{Cl}$ atom can destroy thousands of ozone molecules.