Which one of the following statements is false?
A) Photochemical smog causes irritation in eyes.
B) London smog is a mixture of smoke and fog.
C) Photochemical smog results in the formation of PAN.
D) London smog is oxidising in nature.

Hint: A mixture of smoke which gets stuck in the air with fog in the winter season is known as smog. The sulphurous smog is known as London smog the smog formed due to ultraviolet radiation that reacts to pollutants present in air is known as photochemical smog.

Complete answer:
Photochemical smog results as a photochemical reaction between ultraviolet radiation and the pollutants present in air.
The high concentration of photochemical smog in the atmosphere causes irritation in eyes, headache, throat dryness and chest pain along with multiple respiratory ailments.
Thus, the statement ‘photochemical smog causes irritation in eyes’ is true. Thus, option (A) is not correct.
Classical smog is a mixture of smoke and fog. Classical smog is also known as London smog.
Thus, the statement ‘London smog is a mixture of smoke and fog’ is true. Thus, option (B) is not correct.
The main source of photochemical smog is the burning of fossil fuels. Photochemical smog contains PAN, acrolein and formaldehyde.
PAN is peroxyacyl nitrates.
Thus, the statement ‘photochemical smog results in the formation of PAN’ is true. Thus, option (C) is not correct.
Photochemical smog is oxidising in nature. And London smog is reducing in nature.
Thus, the statement ‘London smog is oxidising in nature’ is false. Thus, option (D) is correct.

Thus, the correct option is (D) London smog is oxidising in nature.

Note: Smog could be seen if there is no wind flowing in the area. The main sources of smog are automobile exhausts, power plants that burn coal, burning of fossil fuels, etc. It usually came from burning coal.