More than $70\; \%$ of the world's freshwater is contained in

$A$ - $BOD$ is a measure of the organic matter present in the water.
$R$ - The lower the $BOD$ of water,the lower is its polluting potential.

Assertion : The concentration of methane in the atmosphere has more than doubled in the last $250$ years.
Reason : Wetlands and rice fields are the major sources of methane.

Explain the importance of the participation of local communities in forest conservation.

Which of the following organisms is likely to have the highest concentration of $D.D.T.$ in its body?

Match the following important dates/events related to environmental issues in India:
$A$. $2002$
$B$. $1$ April $2005$
$I$. Bharat Stage $II$ applicable to all automobiles in the country.
$II$. All buses of Delhi were converted to run on $CNG$.