Which of the following would be categorized as an economic good?

An economic good is defined as a product that is scarce in relation to the demand for it, meaning that it has a price and provides utility or satisfaction to consumers. In this context, the luxury item that provides satisfaction qualifies as an economic good because it is desired by consumers and is limited in availability. This restriction on supply relative to demand ensures that consumers are willing to pay for it, thereby giving it economic value.

In contrast, the other choices do not fit the definition of an economic good. A service that is free to everyone lacks scarcity, as it is provided without charge and is abundantly available. A commonly available resource like air is typically not considered an economic good because it is generally accessible and not limited in most situations, meaning it does not have an associated price in everyday use. Similarly, a good that is abundantly available at no cost also fails to meet the criteria for an economic good, as it has no scarcity and therefore no economic value. This highlights the unique characteristics of the luxury item, which represents both scarcity and the provision of satisfaction.