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When an entity set has several attributes (or attribute sets) each uniquely identifying an entity, each one is called a
Acandidate key; one is then chosen as the primary key
Bforeign key; they reference each other across entity sets
Cpartial key; combined together they form the full key
Dweak key; it identifies entities only within a strong entity
Answer & Solution
Correct answer: A. candidate key; one is then chosen as the primary key
Each minimal uniquely-identifying attribute set is a candidate key. The designer picks one as the primary key, the rest stay candidates. Foreign keys point across entity sets; partial keys identify weak entities only inside their owner; weak key is not a standard term.
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