Chapter 9 - Section 9.2 - The Hyperbola - Exercise Set - Page 981: 4

Graph (c)

Vertices: $(0,1)$ and $(0,-1)$ $ c^2=a^2+b^2=4+1=5$ $ c= \sqrt 5= 2.23$ Foci: $(0, 2.23); (0, -2.23)$ This matches graphs (a) and (c). We choose graph (c) because the value under $x^2$ is larger than the value under $y^2$. Thus, the answer is graph (c).