Which of the following is a biodegradable pollutant?

What does '$X$' represent in the given figure?

Which of the following intensity of sound becomes a pollutant (in $\text{ dB}$)?

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

Which of the following is responsible for the thinning of eggshells in birds?

Match the columns:

Column-$I$	Column-$II$
$(1)$ Electrostatic precipitator	$(a)$ Removes gases like $SO_2$
$(2)$ Scrubber	$(b)$ Reduces automobile emission
$(3)$ Catalytic converter	$(c)$ Removes particulate matter