Final answer:
The number of associations that occur among specific things in an entity relationship diagram is called a relationship.
Step-by-step explanation:
The correct answer is a. a relationship. In an entity relationship diagram (ERD), associations are represented by relationships. A relationship defines the connection or association between two entities. It shows how the entities are related to each other and the nature of the association. For example, in an ERD for a library database, a relationship could be created to show that a student can borrow multiple books.