## Precalculus (6th Edition)

$\emptyset$
RECALL: (1) $\cap$ represents intersection of sets, which is the set that contains the elements that are common to the sets involved. (2) $\emptyset$ represents the empty set, which has no elements. Since $\emptyset$ is empty, then the two set have no common elements. Thus, $\color{blue}{D \cap \emptyset = \emptyset}$