In the stratosphere,ultraviolet radiation is absorbed by ........

In which year was the Montreal Protocol,which aims to protect the ozone layer,signed?

Which of the following acts as a catalyst in the depletion of the ozone layer?

Ozone $(O_{3})$ depletion is due to

The common refrigerant chlorofluoromethane (freon) and $NO_2$ are serious pollutants because

Recognizing the deleterious effects of ozone depletion,an international treaty was signed at Montreal in $1987$ to control the emission of ozone-depleting substances,which is known as $.........$.