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

The ozone layer in the upper atmosphere $(stratosphere)$ is destroyed by which of the following chemicals, or which chemical is responsible for the reduction of the ozone content of the atmosphere?

Which of the following is not caused by $UV-B$ radiation?

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 $.........$.

Explain Ozone Depletion in the Stratosphere.

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