Final answer:
The correct answer to what a primary key for a database is used for is d) Are unique. The primary key ensures that each record in a database table is uniquely identified, allowing for reliable data management. Option D is correct.
Step-by-step explanation:
A primary key for a database table (entity) is used to distinguish each record in a table so that individual records are unique. This is essential because it ensures that each record can be reliably identified and accessed without confusion.
The correct answer to the question is d) Are unique. Each record in a database table must have a unique identifier that is not shared with any other record, and it is the primary key that provides this unique identification. Without a primary key, there would be no way to distinguish between different records if they have similar or identical data in other fields.
In a database table, a primary key is used to distinguish each record in the table so that individual records are unique. This means that no two records in the table can have the same identifier. The primary key serves as a way to identify and access specific records in the table.