Most of the Light from a Galaxy Comes from the Inner

Most of the light from a galaxy comes from the inner parts.If this means that most of the galaxy's mass is also in the inner region,then how would we expect the galaxy's speed of rotation to behave in its outer region?

A) The rotation speed should increase with increasing distance from the center.
B) The rotation speed should decrease sharply to zero at the outer edge of the visible galaxy.
C) The rotation speed should not change appreciably with increasing distance from the center (i.e., a "flat" rotation curve) .
D) The rotation speed should decrease smoothly with increasing distance from the center.