Why Did the Early Earth Differentiate into Core and Mantle

Multiple Choice

Why did the early Earth differentiate into core and mantle?

A) Gravity pulled denser material to the interior and left less dense material on the outside.
B) Nucleosynthesis created an outer mantle layer from fusion of the elements in the core.
C) Gravity first pulled denser material into a protoplanet,and only later was mantle material added.
D) Spinning on its axis caused less dense mantle material to float outside the core.