Describe the Surface Whose Equation in Cylindrical Coordinates Is $\phi = \pi$

Multiple Choice

Describe the surface whose equation in cylindrical coordinates is $\phi = \pi$ .

A) Cylinder with vertical axis
B) Cylinder with horizontal axis
C) Sphere
D) Positive z-axis
E) Negative z-axis
F) Paraboloid
G) Cone or half-cone with vertical axis
H) Cone or half-cone with horizontal axis