Provide an Appropriate Response $\varrho = a \csc \varphi \csc \theta$

Multiple Choice

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

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