In the development of a terrestrial planet, the stage of when dense material settled to the core and less dense to the outer parts. differentiation cratering glaciation accretion flooding

In the development of a terrestrial planet, the stage of differentiation when dense material settled to the core and less dense to the outer parts.  
The stage of planetary differentiation includes separating out different constituents of a planetary body and development into compositionally distinct layers.
It is the organization of the Earth into layers.

The correct answer should be brand c.