Concept:Scarcity occurs because human wants are unlimited, while the resources available to satisfy those wants are limited.Explanation:When demand for a resource is greater than its supply, the resource becomes insufficient to meet everyone's needs.This shortfall between what people want and what is available is the basic condition of scarcity.Scarcity is not caused by an excess of productive resources or supply exceeding demand.Instead, it arises when people's demands outstrip the existing supply of resources.Answer:B. demand for resources is greater than its supply.