#### Answer

$N \cup \emptyset = N$

#### Work Step by Step

RECALL:
(1) $\emptyset$ is the empty set
(2) The symbol $\cup$ represents union of sets which lists down in a set the combined elements of the given sets.
Since the empty set has no elements., then its union with any other set will be the other set itself.
Thus,
$N \cup \emptyset = N$