The Option B is correct.
When ozone near the ground mixes with other polluting gases, then air pollution results in smog.
Smog:
smog is a kind of air pollution, originally named for the mixture of smoke and fog in the air. Classic smog results from large amounts of coal burning in an area and is caused by a mixture of smoke and sulfur dioxide. In the 1950s a new type of smog, known as Photochemical Smog, was first described.