“Ozone hole” means
a) A large-sized hole in the ozone layer
b) Thinning of the ozone layer
c) Small holes scattered in the ozone layer
d) Thickening of ozone in the ozone layer.

Hint: The ozone hole is the depletion of ozone in a region of the ozone layer, over the Antarctica and Arctic poles. It is the depletion in ozone and not complete loss of ozone in the ozone layer.

Complete answer : Ozone is a gas made up of three oxygen atoms, present naturally in the stratosphere in small traces. Whereas in troposphere ozone is created by chemical reactions involving air pollutants from vehicle exhaust, gasoline vapors, and other emissions. The ozone hole does not refer to the literature’s meaning of forming a hole, where no ozone is present. The ozone hole is actually a region of the ozone layer that is exceptionally depleted of ozone causing thinning of the ozone layer. Thus, the ozone hole refers to the thinning of the ozone layer.

Additional information:
>The ozone layer protects the Earth and its living forms from harmful ultraviolet radiations of the sun, when present in the stratosphere but if ozone is present in high concentration near ground level, it is toxic to the living organisms.
>The ozone hole does not lead to global warming but has a huge contribution to climatic changes.

So, Option C is the correct answer.

Notes:Ozone hole is formed due to depletion of the ozone layer and this depletion is due to gases like CFCs (Chlorofluorocarbons), CCl$_4$ (carbon tetrachloride), and CF$_4$ (carbon tetrafluoride). These gases break down the ozone (O$_3$) molecules thus depleting the ozone, leading to the thinning of the ozone layer. The ozone hole is a man-made phenomenon as it’s caused due to gases like CFCs released from spray cans and refrigerants.