What is the process of the depletion of the ozone layer called?

In the following groups of materials,which group$(s)$ contains only non-biodegradable items?
$(i)$ Wood,paper,leather
$(ii)$ Polythene,detergent,$PVC$
$(iii)$ Plastic,detergent,grass
$(iv)$ Plastic,bakelite,$DDT$

What happens during the first step of ozone formation in the atmosphere?

Which of the following are called secondary consumers?

During heavy rain in a village,rainwater carried excessive fertilizers to a pond. How will it affect the fish population in the pond in the long run?

The most important compound which accounts for almost $80\%$ of the total depletion of the ozone layer is $.........$