$BOD$ stands for:

Mention the effects of acid rain.

The ozone layer forms naturally by

$CF_xCly$ [where $x + y = 4$] compounds are not useful because .....

The statements that are $TRUE$:
$A$. Methane leads to both global warming and photochemical smog.
$B$. Methane is generated from paddy fields.
$C$. Methane is a stronger global warming gas than $CO_2$.
$D$. Methane is a part of reducing smog.
Choose the most appropriate answer from the options given below:

Fill in the blanks:
$(1)$ Carbon dioxide is found in the ................. layer.
$(2)$ $A$ high concentration of carbon dioxide is responsible for ................. .
$(3)$ ................. gas is used in air conditioners.
$(4)$ Acid rain causes damage to the ................. monument (wonder).