Water splits during photosynthesis in/on:

Explanation

Water splitting, or photolysis, is a critical step in the light-dependent reactions of photosynthesis. It occurs in the interior space of the thylakoid (thylakoid lumen), where water molecules are split to release oxygen, protons, and electrons. The electrons are then used to replace those lost by chlorophyll in photosystem II. The other options are incorrect because they either describe locations not involved in water splitting or describe processes that occur after water splitting.