Answer: a. spiral arms
Explanation:
Population I contain hot and young stars mostly blue/white in color which are found in the arms of a spiral galaxy. These stars are rich in heavier elements and minerals. Example: Sun is a Population I star found in the Orion arm of Milky way galaxy.
Population II are old stars and clusters. These stars contain lighter elements such as hydrogen and helium. These are fund in globular clusters of milky way and in halo.
