Which of the following is $NOT$ present in photochemical smog?

Identify the odd one out.

Match the following columns:

Column-$I$	Column-$II$
$(a)$ Biomagnification	$(1)$ Nitrates and Phosphates
$(b)$ Eutrophication	$(2)$ Chlorine
$(c)$ Global warming	$(3)$ $DDT$
$(d)$ Ozone depletion	$(4)$ Greenhouse gases

Which of the following statement$(s)$ is/are not correct regarding biomagnification?
$I.$ Heavy metals and persistent pesticides pass into the food chain and increase in amount per unit weight of organisms with the rise in trophic level due to their accumulation in fat.
$II.$ Accumulation of zinc can cause thinning of eggshells in birds.
$III.$ $DDT$ accumulation is a major cause of the killing of fish-eating birds.
$IV.$ Biomagnification occurs only in marine food chains.

Snow-blindness in the Antarctic region is due to

What do '$X$','$Y$',and '$Z$' represent in the given figure respectively?