Charmed by Claire is a successful retail boutique that sells women's accessories. Claire, the owner/manager, knows that women have many options when buying jewelry. When customers enter her store, they are greeted by name and given prompt, friendly attention. Customers return to the store because the service is excellent. Claire says the most important decision she makes is hiring the best staff because customer service is vital to her business. Customer service is a(n): 

core competency. 

organizational resource. 

human resource. 

rare resource.