Which of the following acts is a regulation enforced by the EPA?

The Clean Air Act is a regulation enforced by the Environmental Protection Agency (EPA). This legislation is crucial for controlling air pollution on a national level. It provides the EPA with the authority to establish and enforce air quality standards to protect public health and the environment. Under this act, the EPA regulates emissions of hazardous air pollutants from both stationary and mobile sources, setting limits on various pollutants that can adversely affect human health and the environment.

In contrast, the other acts listed do not fall under the jurisdiction of the EPA. The Fair Housing Act addresses housing discrimination, the National Labor Relations Act focuses on labor rights and collective bargaining, and the Affordable Care Act pertains to health care reform. Each of these acts serves different purposes and is enforced by different governmental agencies or departments, making the Clean Air Act the clear choice for this question.