Assertion (A): Referential integrity is a constraint that defines rules of holding data in parent and child table.

Reasoning (R): Referential integrity ensures that users don't accidently delete or change related data.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Both A and R are true and R is the correct explanation of A.

Explanation
Referential integrity is a constraint that defines rules for maintaining data relationships between parent and child tables in a database. The referential integrity constraint requires that values in a foreign key column must either be present in the primary key that is referenced by the foreign key or they must be null. It ensures the preservation of related data by preventing accidental deletion or modification.