The correct option is Key constraints.

Key constraints are the mechanism that relational databases use to enforce relationships between tables. Primary keys uniquely identify rows in one table and foreign keys reference those primary keys in another table so the database can maintain referential integrity and prevent orphaned or inconsistent records. Databases also use key constraints to enforce rules such as cascade updates and deletes when related rows change.

Table partitions are about dividing a large table into smaller pieces for performance and maintenance and they do not enforce relationships between tables. Partitioning helps with query performance and data management but it does not provide referential integrity.

Columns are the fields that store data and they define the structure of a table. Columns by themselves do not enforce relationships unless they are part of declared key constraints such as primary keys or foreign keys.

Indexes improve query performance by speeding up lookups and joins but they do not by themselves maintain or enforce the logical relationships between tables. Indexes can support the performance of key lookups but referential integrity is provided by key constraints.

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