The Disks of Spiral Galaxies Appear Blue Because

Multiple Choice

The disks of spiral galaxies appear blue because

A) they are moving toward us.
B) they contain a relatively high concentration of low-mass stars.
C) they contain active regions of star formation.
D) they contain more metals that, when ionized, emit blue light.
E) stars collide with each other frequently in these dense regions and explode as Type Ia supernovae.