In Spiral Galaxies, the Tightness of the Winding of the Spiral

Multiple Choice

In spiral galaxies, the tightness of the winding of the spiral arms appears to be related directly to the

A) age of the galaxy, as determined from the age of its individual stars.
B) number of globular clusters in the halo of the galaxy.
C) overall intrinsic size of the galaxy, or the diameter across the spiral arms.
D) size of the central bulge of the galaxy.