Answer
Vertices: $(0,\ 2)$ and $(0, -2)$.
Foci: $(0,\sqrt{5})$ and $(0,-\sqrt{5})$.
Matches graph (a).
Work Step by Step
The transverse axis lies on the y-axis.
$a^{2}=4$
$a=2$
The vertices are $a$ units from the center
$(0,\ 2)$ and $(0, -2)$.
The foci are $c$ units from the center.
$b^{2}=4$
$c^{2}=a^{2}+b^{2}=4+1=5$
$c=\sqrt{5}$
Foci: $(0,\sqrt{5})$ and $(0,-\sqrt{5})$.
Matches graph (a).