Which of the following is true of national ambient air quality standards (NAAQS)?

a. The federal government has the right to enforce NAAQS if the states fail to do so.

b. State governments are responsible for setting standards for air quality in their respective

states.

c. Human beings are protected under the secondary level of NAAQS.

d. Only standards for oxides of elements and particulate matter are evaluated under NAAQS.