Answer to Question 1ANS: C
Heavy elements like iron and nickel pulled inward towards the core while lighter materials like oxygen
and silicon rose toward the surface. The Earth now has distinct interior layers separated by their
density. Information can be found in the section Earth, Ocean, and Atmosphere Accumulated in Layers
Sorted by Density.
Answer to Question 2ANS: D
The Milky Way galaxy is made up of stars, gas, dust, and debris. As with any galaxy, it is held in place
by gravity. The Milky Way galaxy is named after the Greek galaktos, which means milk.
Information can be found in the section Stars and Seas