Final answer:
The Clean Air Act required the use of cleaner-burning gas in cars, leading to a reduction in vehicle emissions and smog in America's cities.
Explanation:
One of the requirements of the Clean Air Act was that cleaner-burning gas had to be used in cars. This led to automakers including catalytic converters on every new car to reduce vehicle emissions by 90 percent. This measure, although slightly raising the cost of new automobiles, contributed significantly to the reduction of smog in America's cities.
Learn more about Clean Air Act and vehicle emissions here:
https://brainly.com/question/42717503
