What Surprising Conclusion About the Distribution of Mass in Our

Multiple Choice

What surprising conclusion about the distribution of mass in our Galaxy has resulted from a study of orbital speeds across the galactic disk?

A) Most of the mass in the Galaxy is dark and is detected only by its gravitational influence.
B) Most of the mass of the Galaxy is in the form of hydrogen gas and giant molecular clouds in the outer region beyond the Sun's orbit.
C) Most of the Galaxy's mass is concentrated in a supermassive nucleus at the center of the Galaxy.
D) Most of the mass in the Galaxy is in the form of O and B stars.