Final answer:
Core competencies represent a costly-to-duplicate economies of scope because they are unique strengths inherent to a company that competitors cannot easily imitate.
Step-by-step explanation:
The question pertains to economies of scope, which is a concept in business that describes the efficiencies that result from a company expanding into new markets or products. When evaluating which of the provided options represents an economy of scope that is costly-to-duplicate, we focus on unique assets or capabilities that are not easily replicated by competitors.
Core competencies are an organization's unique strengths or attributes, including knowledge, experience, and business practices that enable the company to offer superior value to customers and gain competitive advantage. These are difficult for competitors to imitate because they often include cumulative learning and complex interactions among various areas of the organization. So, core competencies best match the description of an economy of scope that is costly-to-duplicate.
In contrast, employee compensation, shared activities, and risk reduction, while important, are generally not regarded as unique and hard-to-replicate elements of a business strategy.