The first of the two distinctive sets of reactions in photosynthesis in which light energy is required to oxidize water and O₂ is released is called:

Explanation

The correct answer is the light reaction, also known as the light-dependent reaction. This process occurs in the thylakoid membranes, where light energy is absorbed by chlorophyll, initiating the photolysis of water. This results in the release of oxygen and the generation of ATP and NADPH. These products are then used in the Calvin cycle to synthesize glucose. The other options, such as the light-independent reaction, Calvin cycle, and dark reaction, refer to the light-independent phase of photosynthesis, which does not directly involve light or the release of oxygen.