Answer: not in A.
- A not in A
- B in A
- C in A ∩ B
- D in the empty set
Correct answer: A. not in A
Explanation: A′ is everything in the universal set U that does not belong to A.
A Venn diagram makes set identities visual: A∪B is everything inside either circle, A∩B is only the overlap, and the region outside both circles represents the complement of their union - directly illustrating De Morgan's law (A∪B)′ = A′∩B′.
Concept context
Types of sets, operations (union/intersection/complement), relations, and types of functions with domain and range