Smog may involve a variety of pollutants.
a. true
b. false

The question is asking us to judge whether the following sentence is correct: Smog may involve a variety of pollutants.This is a true statement: smog means a combination of "fog" and "smoke" and it's whatever pollutants were released into the athmosphere, typically by human activity. Some particles in smog are particularty dangerous to humans, so sometimes the air can be very unhealthy even if on that day it might not seem very grey

Reduction in overall biodiversity