If We Could Watch Spiral Arms from a Telescope Situated

Multiple Choice

If we could watch spiral arms from a telescope situated above the Milky Way over 500 million years, what would we see happen?

A) The spiral arms will eventually dissipate and fade away, since they are a temporary phenomenon that should only last for a million years or so.
B) The spiral arms will eventually unwind, as centripetal forces send the stars flying outwards into intergalactic space.
C) The spiral arms will seem to "wind up," to wrap more and more tightly around the center of the Galaxy.
D) Stars will move through the spiral arms, bunching up closer as they pass through. Young hot stars will form and die within the arms before having a chance to move out.