Which difference between core formation and atmosphere formation in early Earth is correct?

Correct answer: Core formed by density differentiation and atmosphere by outgassing

As early Earth heated and became partly or largely molten, materials separated according to density. Dense metals such as iron and nickel moved inward under gravity and helped form the core, while lighter silicate materials remained above. The early atmosphere developed mainly through outgassing from the interior, especially volcanic release of gases including water vapour, carbon dioxide and nitrogen, with later changes from cooling and other processes. Therefore option B correctly identifies two different mechanisms. The alternatives reverse the materials or incorrectly attribute planetary formation to photosynthesis or modern life.