Which of the Following Fundamental Astronomical Questions Did Curtis and Shapley

Multiple Choice

Which of the following fundamental astronomical questions did Curtis and Shapley debate in 1920 in their famous confrontation?

A) Whether the Sun was at the center of the Milky Way Galaxy
B) Whether the universe was expanding outward in all directions
C) Whether the "spiral nebulae" were part of the Milky Way Galaxy or more distant,separate entities
D) Whether the theory of general relativity could be used to explain the behavior of our universe