What problem arises if irrigation is provided for a long time in fields?

Which of the following is not a pollutant?

Which one of the following represents natural pollutants?

Why is $CNG$ considered a better fuel than diesel?
$(a)$ It cannot be adulterated.
$(b)$ It takes less time to fill the fuel tank.
$(c)$ It burns more efficiently.
$(d)$ It is cheaper.
$(e)$ It is less inflammable.
Choose the most appropriate answer from the options given below:

$A$: High concentration of atmospheric $SO_2$ reduces primary productivity.
$R$: $SO_2$ converts the chlorophyll $a$ into phaeophytin.

$SO_{2}$ pollution affects