Contour farming is usually employed in

The Chipko movement was successfully launched by

Which of the following is not dangerous for life and the atmosphere?

The standard of living is very badly affected by

$A$ lake near a village suffered heavy mortality of fishes within a few days. Consider the following reasons for this.
$A.$ Lots of urea and phosphate fertilizer were used in the crops in the vicinity.
$B.$ The area was sprayed with $DDT$ by an aircraft.
$C.$ The lake water turned green and stinky.
$D.$ Phytoplankton populations in the lake declined initially thereby greatly reducing photosynthesis.
Which two of the above were the main causes of fish mortality in the lake?

The entire fleet of buses in Delhi was converted to $CNG$ from diesel. In reference to this,which one of the following statements is false?