Answer
$B\cup \emptyset= \{ 2,4,6,8 \}$
Work Step by Step
$\bf{\text{Solution Outline:}}$
To get the elements of $
B\cup \emptyset
,$ combine all the elements of $B$ and $\emptyset$.
$\bf{\text{Solution Details:}}$
The union of $B$ and $\emptyset,$ given by $B\cup \emptyset$, are the combined elements of $B$ and $\emptyset$.
With $
B=\{ 2,4,6,8 \}
,$ then
\begin{array}{l}\require{cancel}
B\cup \emptyset= \{ 2,4,6,8 \}
.\end{array}