One Curious Fact About the Milky Way Galaxy,discovered in the Past

One curious fact about the Milky Way Galaxy,discovered in the past few years,is that:

A) a significant fraction of its mass is in the form of globular clusters, distributed in a spherical halo centered on the galactic center.
B) a large black hole is slowly clearing out the mass near the galactic center, leaving a cold, dark void.
C) enormous amounts of energy are pouring out of a compact but very massive source at its center.
D) most of its mass is in the spiral arms extending out into space.