Final answer:
The economic concept that deals with fairness and outcomes is justice, which is closely tied to economic equity, where governments redistribute wealth to ensure fair opportunities and support for low-income families. It contrasts with economic efficiency, related to optimal resource use. The correct option is D.
Step-by-step explanation:
The concept in question that deals with fairness and outcomes in economic theory, especially in regard to regulation, is justice. This is evident in discussions of economic equity, where the government plays a role in redistributing wealth to promote fairness, for example through progressive taxation or social welfare programs.
These actions are taken to assist low-income families with essential services like food, housing, medical care, and education grants. Conversely, economic efficiency focuses on the optimal utilization of resources without waste, aligning prices with marginal costs, as seen in effectively competitive markets and regulatory interventions aiming to ensure such efficiency for the greater social benefit.