Approximately $P$ fraction of the solar radiation reaching the Earth is reflected by clouds and gases,and another $Q$ fraction is absorbed by them.

Which of the following refers to the increase in the concentration of a toxicant at successive trophic levels?

Select the correct statement regarding conventional chemical farming methods.

$A$ 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?

Which of the following is a non-renewable resource?

Which of the following pairs is correctly matched?