I think (B) is also correct option. what is your opinion ?
yes AUB⊆A∩B iff |A| should be equal to |B|.
I think |A| = |B| is incorrect but A=B is correct. So AUB⊆A∩B iff A=B.
@ Chhotu i mean if AUB⊆A∩B then A=B
so when A=B then both should have same cardinality so |A| = |B|..please correct me if i am wrong!