Final answer:
Welfare-promoting groups are interest groups that lobby for certain populations needing better protections and advocacy, such as labor unions.
Step-by-step explanation:
The kind of interest group that lobbies on behalf of certain segments of the population, aiming to ensure better protections and advocacy, are generally known as welfare-promoting groups. These groups actively engage in lobbying to influence public policies for the benefit of specific segments in society that they believe require greater support and representation. An example would be labor unions, such as the Service Employees International Union, which fight for collective bargaining rights, better wages, and working conditions on behalf of their members.