Which type of entity instances can store attributes that are common to one or more entity subtypes?

The correct answer is the supertype. A supertype is an entity that contains attributes that are shared by its subtypes. By defining a supertype, you establish a common structure for its subtypes, allowing for data normalization and efficient data management. This means that any attributes that are applicable across multiple subtypes can be centralized in the supertype, reducing redundancy and making the data model cleaner and more maintainable.

For instance, if you have an entity representing "Vehicle" as a supertype, and specific subtypes like "Car" and "Truck," attributes such as "make," "model," and "year" can be stored in the Vehicle supertype. This way, both Cars and Trucks inherit these attributes without needing to redefine them separately for each subtype.

In contrast, subtypes are specific entities that inherit characteristics from their supertype, derived types are entities that are calculated from other data, and composite types refer to data structures that consist of multiple elements, none of which fits the description of storing common attributes for subtypes.