(i) Both A and R are correct and R is correct explanation of A.

Explanation: Ozone formation takes place in the stratosphere when dioxygen reacts with free Oxygen in the presence of intense UVradiations. This ozone layer protects the Earth from the harmful radiations coming from the Sun, otherwise which cause several severe medical problems like melanoma (skin cancers) inhumans. At the same time, ozone is unstable thermodynamically,therefore, as soon as it is formed it gets decomposed tomolecular oxygen in the stratosphere. Although, this process of decomposition is being accelerated due to the usage of various anthropogenic activities or release of CFCs/freons. These chemicals are used in refrigerators, ACs etc and are non-reactive, non-toxic and non-flammable to humans but still due to the ability to produce Cl radicals continuously upon reacting with UV in the stratosphere, they contribute in the depletion or thinning ofthe ozone layers.

This reaction takes place continuously thereby resulting in destroying or scavenging ozone molecules. Thus, leading to thinning of ozone layer.