Assertion. The foreign-keys of tables are used to establish relationships with other tables and must be handled carefully.

Reason. Referential integrity is a system of rules that a DBMS uses to ensure that the relationships between tables remain valid and no accidental change or deletion occurs in the related data.

(a)

Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

Explanation
The foreign keys of tables are utilized to establish relationships with other tables, while referential integrity is a system of rules that a DBMS employs to ensure the validity of relationships between records in related tables. This system prevents users from accidentally deleting or changing related data. Therefore, it is crucial to handle foreign keys carefully.