Answer is [C] Owner Entity set.
Owner entity Set : Weak entities are identified by being related to specific entities in combination with one of their attribute values. We call this other entity type the identifying or Owner entity type. ex : DEPENDENT(Name, Age, Gender, relationship) and EMPLOYEE. Here DEPENDENT is weak entity as it does not have key attribute. There may be a chance that two employees can have dependents with same name, same age, same gender, same relationship.
Why not Strong entity set ?
Bcoz, Strong entity type is an entity which has key attribute.