Pick up the one not involved in the cyclic electron flow of the light reaction of photosynthesis:

Explanation

In cyclic photophosphorylation, electrons excited by light in Photosystem I are cycled back through a specific chain of carriers to generate ATP without the production of NADPH or oxygen. The electron flow proceeds from Photosystem I to ferredoxin, then to plastoquinone (PQ), and through the cytochrome b6f complex, before returning to Photosystem I. This cycle helps build a proton gradient used by ATP synthase to produce ATP. However, plastocyanin does not participate in cyclic photophosphorylation; instead, it functions in non-cyclic photophosphorylation, where it transfers electrons from Photosystem II to Photosystem I. Therefore, plastocyanin is the component not involved in the cyclic electron flow of photosynthesis.