Referential key is the correct answer to the given question .
Explanation:
The Referential key is also known as foreign key .In the Referential key the foreign key table field must be match with the field of primary key table in another table .
The main objective of Referential key providing the interaction between the two tables also the Referential key is provides the concept of referential integrity .
Primary key is used find the unique record in the database they are not created when the two tables contain the common field so that's why it is incorrect option.
Key template and Relationship are not providing the linking between the two tables that's why it is incorrect option .
