Soil conservation can be best achieved by having

The Bhopal gas tragedy occurred in $1984$ because methyl isocyanate reacted with .......

What human activities are responsible for the increase in the amount of $CO_2$ in the atmosphere?

Consider the following statements:
$I.$ Reforestation is the process of restoring a forest that once existed but was removed at some point of time in the past.
$II.$ Reforestation may occur naturally in a deforested area.
$III.$ $A$ tree plantation movement or Van Mahotsava is being carried out in India since $1982$.
Which of the statements given above are correct?

In the $1990s$,Delhi ranked ............. among the ...... most polluted cities of the world.

$A$: $El$ $Nino$ is a climatic change which causes deleterious environmental changes.
$R$: Increased tropospheric ozone due to $El$ $Nino$ causes a shift of climatic regions.