Which of the following properties should be satisfied when the identifier of the entity type becomes the primary key of the corresponding relation?

Which of the following properties should be satisfied when the identifier of the entity type becomes the primary key of the corresponding relation?
A) The value of the key must uniquely identify every row in the relation.
B) The key should serve as a foreign key in at least two other relations.
C) The key must be a composite of a primary key and a secondary key.
D) The key should be an intelligent key.
E) The key should allow for null values.
Answer :

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