Which operation does not guarantee referential integrity?

The operation that does not guarantee referential integrity is associated with the concept of ignoring certain relationships or constraints within a database's foreign key references. When you choose to "ignore," it means that the system will not enforce any rules regarding the integrity of the relationships between tables. This can lead to a situation where records in a child table may reference records in a parent table that no longer exist, effectively violating the principles of referential integrity.

In contrast, the other operations, such as protecting and deleting records, usually involve mechanisms that ensure the integrity of the data. For example, "protect" often refers to various methods through which the database prevents actions that would compromise these relationships, such as restricting the deletion of a record in a parent table if there are dependent records in child tables. Deleting, on the other hand, typically involves checks to ensure that the referential integrity is maintained when removing records, possibly through cascading deletes or blocking actions that would orphan records.

Thus, the reason for identifying the option pertaining to ignoring as the correct answer lies in the essence of what it means to operate with respect to referential integrity—the option to ignore explicitly negates any enforcement of those relationships, leading to potential data inconsistencies.