In 1948 in donora, pennsylvania, the routine release of toxins into the air became a deadly fog because of

In the year 1948 in Donora (Pennsylvania) smog killed 20 people and sickened about 7,000. The sulfuric acid, nitrogen dioxide and other toxic gases were caught in the thermal inversion and accumulated. It was one of the worst air pollution disasters in the history.  C ) a thermal inversion and stagnant weather conditions.