Which among the following has the highest concentration of $PAN$?

What is Eutrophication?

Acrolein $(X)$ is one of the chemicals formed when $O_3$ and $NO_2$ react with unburnt hydrocarbons present in the polluted air. The structure of '$X$' is

Biochemical Oxygen Demand $(BOD)$ is the amount of oxygen required (in $ppm$):

The statement that is not true about ozone is:

The secondary precursors of photochemical smog are