What Is the Dilemma About the Spiral-Arm Structure of a Typical

What is the dilemma about the spiral-arm structure of a typical spiral galaxy?

A) The measured speeds of stars in the galaxy are exactly correct for the present spiral structure, having spun the observed tightness of the spiral in the typical lifetime of a galaxy.
B) If the measured speeds of stars in the galaxy had spun the arms into shape, these arms would be far less tightly wound than the observed arms.
C) If the measured speeds of stars in the galaxy had spun the arms into shape, these arms would be far more tightly wound than the observed arms.
D) The measured speeds of material in the spiral arms should not have led to any spiral but should have generated a straight bar rotating like a solid object.