Question

which photosystem(s) pass(es) protons across the thylakoid membrane into the lumen?
both photosystems i and ii
photosystem ii
photosystem i
neither photosystem i nor ii

Explanation:

In the light - dependent reactions of photosynthesis, photosystem II is involved in the process of passing protons across the thylakoid membrane into the lumen as part of the electron - transport chain. Photosystem I is mainly involved in the production of NADPH and not in proton pumping across the thylakoid membrane into the lumen.

Answer:

B. photosystem II