Which of the following is true for photochemical smog?

Classical smog is formed by the combination of smoke, dust and fog containing sulphur dioxide from polluted air. This is also called chemical smog. Chemically, it is a reducing mixture, and so it is also called reducing smog. Photochemical smog is formed by the combination of smoke, dust and fog with an air pollutant in the atmosphere as a result of a photochemical reaction. The chemistry of the formation of photochemical smog centres around nitric oxide (NO). $N{O}_2$ again absorbs UV radiations and the entire cycle starts again. Both $N{O}_2$ and $O_3$ are strong oxidizing agents and can react with unburnt hydrocarbons (from the exhaust of automobiles) to form organic free radicals. The formation of organic free radicals results in a number of chain reactions producing many undesirable compounds (such as formaldehyde, acrolein, organic peroxides, organic hydroperoxides, peroxyacyl nitrates etc.) which constitute photochemical smog. It also includes $H_2{O}_2$. The brownish haze of photochemical smog is largely due to the brown colour of $N{O}_2$.