Identify the sphere where life first emerged on earth.

The correct answer is - Hydrosphere.

Life on Earth, emerged in the hydrosphere, at least from the findings and data so far. The reason for that was that the atmosphere and the lithosphere were still in a faze were they were not very hospitable for any living organisms to develop. The hydrosphere, or the water bodies, on the other side, were enabling conditions for life, not perfect or as we have today, but still reasonably good, so the life started developing into the water environment, and after the atmosphere and lithosphere changed over time, it spread on them as well.