Which photosystem is a chlorophyll-protein complex that uses light energy to release excited electrons?

Photosystem II is the chlorophyll-protein complex primarily responsible for capturing light energy and using it to energize electrons, which are then released. This complex contains chlorophyll a, along with other pigments, which absorb light, particularly in the blue and red wavelengths.

When light energy is absorbed by Photosystem II, it excites electrons that are stored in chlorophyll molecules. These energized electrons are then transferred to an electron transport chain, initiating the process of photophosphorylation and ultimately leading to the synthesis of ATP and NADPH. Additionally, Photosystem II plays a crucial role in water-splitting, producing oxygen as a byproduct.

The other options either do not directly relate to the initial absorption of light energy or are not involved in the same way in the photolysis of water and electron excitation. Thus, Photosystem II stands out as the correct answer for its specific role in utilizing light energy to release excited electrons in photosynthesis.