Answer: D. The olivine became the crust and the Iron melting defended the earth to become the core.
Step-by-step explanation:
Earth was formed after it has went through a molten stage that led to the heavy materials sure as Iron metal moving inward to form the core, and the light materials moves toward the surface to form the crust.
The heat for the melting came from meteorite impacts which is usually very hot, the moon's impact, and the decay of radioactive elements.
Geological activity on the earth is driven from this initial source of heat at the earth's formation until now.