Which of the following statements about the depletion of ozone layer is correct?

The problem of ozone depletion is less serious at poles because $\displaystyle \mathrm{NO}_2$ solidifies and is not available for consuming $\displaystyle \mathrm{ClO}^{\bullet}$ radicals.

The problem of ozone depletion is more serious at poles because ice crystals in the clouds over poles act as catalyst for photochemical reactions involving the decomposition of ozone by $\displaystyle \mathrm{Cl}^{\bullet}$ and $\displaystyle \mathrm{ClO}^{\bullet}$ radicals.

Freons, chlorofluorocarbons, are inert chemically, they do not react with ozone in stratosphere.

Oxides of nitrogen also do not react with ozone in stratosphere.