If the $pH$ of water increases above ......,the effectiveness of chlorination in water is reduced.

Statues and monuments in India are affected by acid rain. How?

Provide the correct statement for the following: (Use $T$ for True and $F$ for False statements.) $(1)$ Plants obtain elements like carbon,hydrogen,and oxygen from air and water. $(2)$ Plants obtain elements like $N, P, K, Ca$ from the soil. $(3)$ Compound fertilizers contain nitrogen as ammonium nitrate,phosphorus as $PCl_3$,and potassium as $KO_2$. $(4)$ The use of $NPK$ fertilizers increases the production of crops and vegetables in the soil.

What are pesticides and herbicides? Explain giving examples.

Match the water pollutants given in List-$I$ with their sources given in List-$II$.

List-$I$	List-$II$
$A$. Toxic heavy metals	$1$. Soil erosion from agricultural and mineral industries.
$B$. Pesticides	$2$. Domestic sewage disposal.
$C$. Sediments	$3$. Chemical factories and industries.
$D$. Microorganisms	$4$. Substances used to kill insects,fungi,and weeds.

In the stratosphere,most of the ozone formation is assisted by: