For a Unary M:N Relationship

For a unary M:N relationship:

A) the entity type is modeled as one relation;using as its primary key a composite key,a separate relation is created to represent the M:N relationship
B) the entity type and the M:N relationship are modeled as one relation;a composite key is used
C) separate relations for the class and for each subclass are created;primary and foreign keys are established for each class
D) the primary key of the entity on the one side of the relationship serves as a foreign key in the relation on the many side of the relationship