The primary key is selected from the:
Option C. Candidate Keys.
Candidate key is a set of attributes that uniquely identify tuples in a table.
We can have more than one candidate keys for a relational schema.
Any one of the key is chosen from candidate key as Primary Key.
CANDIDATE KEY is a set of attributes that uniquely identify tuples in a table. Candidate Key is a super key with no repeated attributes. The Primary key should be selected from the candidate keys. Every table must have at least a single candidate key. A table can have multiple candidate keys but only a single primary key.
Option C is Correct
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