Q.Which is considered to be earth's protective umbrella? Why?

Stratospheric pollution refers to the chemical destruction of the protective ozone layer, which normally exists in a dynamic equilibrium between UV-driven formation from O2 and natural decomposition back to O2. The main destructive agents are chlorofluorocarbons (CFCs), unreactive industrial chemicals that survive long enough to reach the stratosphere, where UV radiation splits them to release chlorine free radicals. Each chlorine radical destroys ozone and is regenerated in a self-sustaining chain reaction, so one CFC molecule can destroy vast numbers of ozone molecules. Over Antarctica this produces a seasonal ozone hole: in winter, polar stratospheric clouds allow chlorine reservoir compounds to convert into reactive chlorine forms, which are …