What uniquely identifies a given entity in a database table?

A primary key is a unique identifier for a given entity in a database table. It ensures that each record within that table can be distinctly recognized and referenced, preventing duplication of data. The primary key enforces entity integrity by providing a means to uniquely distinguish each row within that table, which is essential for maintaining accurate and efficient database relationships.

When a primary key is defined for a table, it can consist of a single column or a combination of columns, depending on the specific requirements for unique identification within that dataset. This uniqueness allows for efficient querying of records, relationships with other tables, and overall data integrity throughout the database.

Other options, such as a foreign key, are designed to establish relationships between tables rather than to uniquely identify a record within a single table. An index improves the speed of data retrieval but does not confer any uniqueness. A record ID, while it might refer to a unique identifier, is not a formal database term and is not synonymous with the primary key concept. Thus, the primary key stands out as the correct answer in ensuring that each entity in a table is uniquely identifiable.