D. A public interest group is the type of interest group that would lobby Congress to pass new laws that regulate the carbon emissions of coal power plants in order to improve air quality.
Public interest groups are organizations that advocate for policies and legislation that promote the general public good or the common interest. They typically focus on issues such as consumer protection, environmental protection, and social welfare, and often represent the interests of groups or individuals who may not have the resources or political power to do so themselves. In this case, a public interest group focused on environmental protection would be most likely to lobby Congress to pass new laws regulating carbon emissions from coal power plants in order to improve air quality.