For a Unary One-To-One Relationship Between Two Entities a and B

Multiple Choice

For a unary one-to-one relationship between two entities A and B, the relationship is represented by:

A) adding the primary key of A as a foreign key of B.
B) adding the primary key of B as a foreign key of A.
C) combining the two entities into one relation.
D) creating a third relation to represent the relationship between the two entities.
E) either A or B.