Continued volcanism after crust formation clarifies which distinction?

Correct answer: Cooling of outer surface and activity of interior

The direct answer is A: the outer surface could cool and solidify while the interior remained hot and geologically active. Earth did not lose all its heat as soon as a solid crust formed. Heat left over from planetary formation, along with heat released by radioactive decay, remained inside the young Earth. This internal heat helped maintain melting, movement of molten material, and convection below or within the crust. When magma rose through cracks and reached the surface, volcanism continued even though the outside had become comparatively cool and solid. Option A correctly describes this contrast between the crust and the interior. B is about different forms or roles of oxygen and has no connection with magma. C compares two water bodies and does not explain volcanic activity. D compares a solar phenomenon with rainfall and is also unrelated. A useful memory cue is: “Cool shell, hot engine”—a solid outer shell does not prove that the inside is inactive.