What do we call a superkey?
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When a field that is a primary key cannot be used a foreign key because of security policies
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When a primary key is composed by more than field
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When a primary key is a set of fields that are foreign keys
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When a set of fields that are foreign keys are set as a primary key
A superkey is a set of one or more attributes that can uniquely identify tuples in a relation. The question describes a composite primary key (one made of multiple fields) but calls it a 'superkey' - this is terminology confusion. A composite primary key IS a type of superkey, but the standard definition doesn't mention security policies or foreign keys. The question's phrasing is imprecise but option B is the closest to describing a multi-attribute key.