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

Which day is celebrated as World Ozone Day?

$CFCs$ are not recommended to be used in refrigerators because they

World Ozone Day is celebrated on

Which of the following statement$(s)$ is/are correct?
$(i)$ The Montreal Protocol was signed in $1987$ and became effective in $1989$.
$(ii)$ 'Good' ozone is found in the troposphere.
$(iii)$ Ozone is formed by the action of $UV$ rays on molecular oxygen and degrades into molecular oxygen.
$(iv)$ $CFCs$ are responsible for the imbalance between the production and degradation of ozone.
$(v)$ $DNA$ and proteins of living organisms absorb $UV$ rays.

What was the purpose of the $Montreal$ $Protocol$?