Which one of the following is responsible for depletion of the ozone layer in the upper strata of the atmosphere? (AIPMT 2004)

Chlorofluorocarbons such as freon-11 (CFCl3) and freon-12 (CF2Cl2) emitted as propellants in aerosol spray cans, refrigerators, fire fighting reagents etc. are stable compounds and chemically inert. They do not react with any substance with which they come in contact and thus float through the atmosphere unchanged and eventually enter the stratosphere. There they absorb UV radiations and break down liberating free atomic chlorine which causes decomposition of ozone. This results in the depletion of the ozone layer. 3 2 3 2 Cl O ClO O ClO O Cl O -> ->