At the beginning of the $20^{th}$ century,forests covered about $.....P.....$ of the land in India. By the end of the century,this had shrunk to $.....Q.....$.

Polyblend is made using $..............$.

List all the wastes that you generate at home,school,or during your trips to other places. Which could you very easily reduce? Which would be difficult or rather impossible to reduce?

$A$: $A$ few toxic substances often present in industrial waste waters undergo biological magnification.
$R$: $A$ toxic substance can easily be metabolised or excreted by an organism.

Given below are two statements.
Statement $I$ - Algal blooms impart a distinct color to the water bodies.
Statement $II$ - Some bloom-forming algae are extremely toxic to fishes but not to human beings and other animals.
In the light of the above statements,select the correct option:

What is the effect of $Pb$ (lead) on catalysts?