For a binary relationship set R between entity sets A and B$,$ the Mapping Cardinality is ONE TO ONE if

A

An Entity A is associated with any number $($zero or more$)$of entities in B$,$ An entity in B however, can be associated with at most one entity in A$.$

B

An entity in A is associated with at most one entity in B$,$ and an entity in B is associated with at most one entity in A

C

an Entity A is associated with at most one entity in B$,$ An entity in B however, can be associated with any number zero or more of entities in A