The main component of photochemical smog is ans. Oxides of nitrogen All of the above Water vapour Sulphur dioxide

The main component of photochemical smog is Oxides of Nitrogen.

Photochemical smog, often referred to as "summer smog", is the chemical reaction of sunlight, nitrogen oxides and volatile organic compounds in the atmosphere, which leaves airborne particles and ground-level ozone. This noxious mixture of air pollutants can include the following:

1. Nitrogen oxides, particularly nitric oxide and nitrogen dioxide
2. Volatile organic compounds, often from burned fossil fuel
3. Peroxyacyl nitrates
4. Tropospheric ozone
5. Aldehydes

So, while Sulphur dioxide, Water vapour, and other components can be part of smog, the main component that leads to the creation of photochemical smog is Oxides of Nitrogen.