If one exists, a data modeler uses a as the primary key of the entity being modeled. select one: a. foreign key b. combination key c. surrogate key d. natural identifier

The correct answer is letter "D": natural identifier.

Explanation:

Natural identifiers are pieces of real information from people or entities that are registered in a database. This information is considered unique such as social security numbers, e-mail addresses, or any other identification that only one individual must possess. While creating or identifying a data modeler natural identifiers are used as the main resource of those modelers being set up.

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