What Has Microlensing Told Astronomers About the Role of Brown

What has microlensing told astronomers about the role of brown dwarfs in the Milky Way Galaxy?

A) Brown dwarfs cannot be a major component of the dark matter in the Galaxy.
B) Brown dwarfs are a major component of the matter that is falling into the supermassive black hole in the galactic center.
C) Brown dwarfs are one of the most important components of the Galaxy's dark matter.
D) Microlensing has stated almost nothing yet about brown dwarfs-microlensing is too difficult to observe.