01 If A ⊆ B, then A ∪ B is equal to what?
Answer and explanation
Correct answer: B. B
Explanation: The relation A ⊆ B means that every element of A is already an element of B. The union A ∪ B contains all elements that belong to A or B. Since A contributes no element outside B, taking the union adds nothing to B. Therefore, A ∪ B = B. Notice that A ∩ B = A, but the question asks for the union, so option B is correct.