Answer:
The correct answer is - photosystem II.
Explanation:
Photosystem II is a specialized protein complex that traps the light energy from the sunlight and utilizes it to transfer electrons to Pq from water, which ultimately helps in the production of oxygen.
As we know photosystem II helps in production and cyanobacteria were the primitive organism it is considered as after the development of the photosystem II, cyanobacteria begin the aerobic life.
Thus, the correct answer is - Photosystem II.