If X⊆YX \subseteq YX⊆Y and Y⊆ZY \subseteq ZY⊆Z, which of the following statements must be true for any sets X,Y,X, Y,X,Y, and ZZZ?
X⊆ZX \subseteq ZX⊆Z
X∩Z=∅X \cap Z = \emptysetX∩Z=∅
X∪Z=YX \cup Z = YX∪Z=Y
Z⊆XZ \subseteq XZ⊆X