Answer: 3.
- A 3
- B 4
- C 2
- D 1
Correct answer: A. 3
Explanation: A 2-element set has 2² = 4 subsets, so 4 − 1 = 3 proper subsets.
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