Which of the Following Is True About the Clean Air

Which of the following is true about the Clean Air Act?

A) Congress established national ambient air quality standards for a number of pollutants.
B) Congress set goals, but not standards, for a number of pollutants.
C) Congress directed the Environmental Protection Agency to set ambient air quality standards for certain pollutants, but the Environmental Protection Agency has not yet set the standards, due to scientific uncertainty.
D) Congress directed the Environmental Protection Agency to set ambient air quality standards for certain pollutants, and standards have been set thus far for carbon monoxide and sulfur oxide, among others.
E) Congress ordered the states to set ambient air quality standards, and most states have thus far set at least some ambient air quality standards.