Population i stars are found in what area of the milky way?
a. spiral arms
b. central bulge
c. halo
d. globular clusters

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.

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.

the correct answer is:

a population changes in response to a change in the environment.