Converting a One-To-One Unary Relationship into a Relational Database from an E-R

Multiple Choice

Converting a one-to-one unary relationship into a relational database from an E-R diagram ____.

A) can be done by adding another copy of the unique identifier of the single entity's table into the same table with a different attribute name
B) can be done by splitting the attributes of the single entity into two tables, each with its own copy of the unique identifier
C) requires the creation of an additional table beyond the one that represents the single entity in the relationship
D) a & b above
E) a & c above