_ Use of a supertype/subtype relationship is necessary when which of the following exists?$?

• A. An instance of a subtype participates in a relationship that is unique to that subtype.
• B. An instance of a subtype participates in a relationship that is the same as the other subtypes.
• C. Attributes apply to all of the instances of an entity type.
• D. No attributes apply to any of the instances of an entity type.