If A⊆BA \subseteq BA⊆B, which of the following is always true?
A∪B=BA \cup B = BA∪B=B
B∖A=∅B \setminus A = \emptysetB∖A=∅
A∖B=AA \setminus B = AA∖B=A
A∩B=BA \cap B = BA∩B=B