Explanation

B is correct because photochemical smog primarily forms from nitrogen dioxide and hydrocarbons reacting in sunlight. A is incorrect because SO2 and CO2 are not the main constituents of photochemical smog. C is incorrect because while NO2 is a component, CO2 is generally not listed as a primary constituent alongside it for this type of smog. D is incorrect because CFCs are more associated with ozone depletion rather than being a primary constituent of typical photochemical smog mixtures.