The correct answer to this question is A, Referential integrity is enforced. This is a concept related to relational databases. The concept states that the table and their relationships must always be consistent. Another way to explain referential integrity is that foreign keys must always agree with the primary keys.
In the same token, any primary key must always match the foreign keys. Its purpose is to prevent orphans, as well as keep the sync of references. It prevents any necessary information from being deleted, and the record no longer exists. It would be used in the Microsoft software Microsoft Access.