A Rotation Curve Is a Plot of the Rotational Velocity

A rotation curve is a plot of the rotational velocity of a galaxy as a function of the distance away from the galactic center. What does the rotation curve of the Milky Way Galaxy look like?

A) The curve is a straight line, slanted upward, suggesting that the velocity increases linearly with radius.
B) The curve rises steeply, levels off, and then experiences the "Keplerian falloff" expected from Kepler's third law.
C) The curve rises steeply and then oscillates up and down showing the effect of the spiral arms.
D) The curve rises steeply, and then levels off or rises gradually until well beyond the edge of the visible galaxy.