## Precalculus (6th Edition)

$B$
RECALL: (1) $\cup$ represents union of sets, which is the set that contains the combined elements of the sets involved. (2) $\emptyset$ is the empty set, which has no elements. Since $\emptyset$ is empty, then the union of the two given sets will just be the non-empty set $B$. Thus, $\color{blue}{B \cup \emptyset = B}$