Referential integrity

Referential integrity refers to______________

A) The enforced uniqueness of a row in a table
B) The enforced uniqueness of a column in a table
C) Ensuring that a Foreign Key attribute cannot be NULL
D) The enforced synchronization of Primary Key and Foreign Key values

i say is D the answer mainly because that way you ensure the integrity of data by, for example, avoiding orphan records and is part of the basis of db relational theory.
however, this question is hard because of A.
thus, if this is multiple choice, i definitely say is A and D.
however, if this choosing only one answer, i say this is definitely D.

best regards,

tonci korsano