Good tracers of the spiral arms of our galaxy are all
I.very old.
II.very young.
III.very luminous.
IV.moving with large radial velocities.
A)I & III
B)I & IV
C)II & III
D)II & IV
E)I, III, & IV

Question

Good tracers of the spiral arms of our galaxy are all 
I.very old.
II.very young.
III.very luminous.
IV.moving with large radial velocities.
A)I & III
B)I & IV
C)II & III
D)II & IV
E)I, III, & IV

Quizplus · Accepted Answer

II (very young) and III (very luminous) are good tracers of the spiral arms of our galaxy because young, luminous stars are typically found in these regions, marking the spiral patterns.

Good Tracers of the Spiral Arms of Our Galaxy Are