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The populations become completely separated from one another</span>
Answer:
You should conduct more research and assume that the text book may have incorrect information!
Explanation:
<span>the spiral arms of the milky way was made of: D. younger stars and gaseous nebulae
The spiral arms of the mily way was organized into four spiral arms, and since it was made of younger stars and gaseous nebulae, Spiral arms typically contain a higher density of interstellar gas and dust than the Galactic average as well as a greater concentration of star formation</span>
