For a weak entity set to be meaningful, it must be associated with another…

Answer: Owner Entity Set

Explanation: A weak entity set cannot be uniquely identified by its own attributes alone. It must be associated with another entity set (the owner entity set) through an identifying relationship. The weak entity’s identity is formed by combining its partial key with the primary key of its owner.

• Identifying relationship: The relationship that links the weak entity to its owner and supplies part of its key.

• Key composition: Weak entity primary key = (owner primary key) + (weak entity partial key).

• Ownership: The owner entity set is often required to have a total participation of the weak entity in the identifying relationship (weak entity cannot exist without the owner).

Short example: If Dependents is a weak entity with partial key Name and Employee is the owner with primary key EmployeeID, then the Dependents primary key becomes (EmployeeID, Name).

Why other choices are wrong: The term "Strong Entity Set" refers to entities that have an independent primary key; "Weak Set" names the dependent set itself rather than the associated owner; "Neighbour Set" is not a standard term in this context.