How Many Stars Per Cubic Parsec Are There in the Spiral

Multiple Choice

How many stars per cubic parsec are there in the spiral arms of a spiral galaxy compared with the regions between the spiral arms?

A) The density of stars inside spiral arms is more than 100 times that in the regions between the arms.
B) The density of stars inside spiral arms is about twice that in the regions between the arms.
C) There are a lot of stars in the spiral arms and none at all in the regions between the arms.
D) The density of stars inside spiral arms is about 5% more than in the regions between the arms.