List the Elements of the Set $A = \{ x \mid x$

Multiple Choice

List the elements of the set.
-If $A = \{ x \mid x$ is an odd integer $\}$ and $B = \{ 51,53,54,56 \}$ , list the elements of $A \cup B$ .

A) { }
B) $\{ x \mid x$ is an odd integer $\}$
C) $\{ 51,53 \}$
D) $\{ x \mid x$ is an odd integer or $x = 54$ or $x = 56 \}$