Geologists now believe that the Earth's three-layer structure, as shown in the table below, owes much to the interactions between heat and materials with different properties. Layer of Earth Average Density
(g/cm3)
crust 2.7–3.0
mantle 4.5
core 11

Which theory below explains why the Earth is composed of three layers of varying density?
A.
The early Earth was struck by an asteroid, which became the core as it pushed up the mantle and core.
B.
The orbit of the early Earth brought the planet closer to the Sun, which increased its internal energy.
C.
When Earth was molten, heavier materials sank to the center as lighter materials rose to the surface.
D.
When Earth was molten, lighter materials sank to the center as heavier materials rose to the surface.