What was the combined effect of meteorite impacts and radioactive decay on early Earth?

Correct answer: Heat increase and possibility of internal differentiation

The governing concept is the thermal evolution and internal differentiation of the early Earth. During its formation, repeated impacts by planetesimals and meteorite-like bodies converted kinetic energy into heat. Radioactive decay inside the young planet supplied an additional internal heat source. Together, these processes helped keep the early Earth partly molten or highly heated for a long period. In such conditions, denser materials such as iron could move downward while lighter silicate materials rose, creating the possibility of layered internal structure. Option A is correct because it states both the heating effect and its consequence for differentiation. Option B is unrelated and much too immediate, while options C and D do not follow from these heat-producing processes.