Provide an Appropriate Response $\varrho = a \csc \varphi$ B) $\varrho = a \sin \varphi$

Multiple Choice

Provide an appropriate response.
-What form do planes perpendicular to the z-axis have in spherical coordinates?

A) $\varrho = a \csc \varphi$
B) $\varrho = a \sin \varphi$
C) $\varrho = a \cos \varphi$
D) $\varrho = a \sec \varphi$