In the light reactions of photosynthesis, what is P680?

• A. The reaction-center chlorophyll a special pair in Photosystem II that absorbs light most efficiently at about 680 nm
• B. The reaction-center chlorophyll a special pair in Photosystem I that absorbs light most efficiently at about 700 nm
• C. The mobile electron carrier that transfers electrons from Photosystem II to the cytochrome $b{f}_6$ complex
• D. The enzyme complex that splits water to release oxygen, electrons, and protons (oxygen-evolving complex)

Answer: (A)