Answer:
d. NADPH : ATP : oxygen
Explanation:
Light acts on the P700 molecule of Photosystem I, causing an electron to be elevated to a higher potential. This electron is accepted by a primary acceptor (different from the one associated with Photosystem II).
The electron again goes through a series of redox reactions, and is eventually combined with NADP+ and H+ to form NADPH, an H-carrier needed in the light-independent phase.
Photosystem electron II replaces the excited electron of the molecule P700. There is therefore a continuous flow of electrons (non-cyclic) from water to NADPH, which is used for carbon fixation.
The cyclic flow of electrons occurs in some eukaryotes and photosynthetic bacteria. NADPH, only ATP, is not produced. This also occurs when the cell requires additional ATP, or when there is no NADP+ to reduce it to NADPH.
In Photosystem II, the H-ion "pumping" inwards of the thylacoids (from the chroma of the chlorotoplast) and the conversion of ADP+P into ATP is motorized by an electron gradient established in the thylacoid membrane.
The energy of light causes the removal of an electron from a P680 molecule that is part of Photosystem II, the electron is transferred to an accepting molecule (primary acceptor), and then passes downhill to Photosystem I through a conveyor chain of Electrons. The P680 requires an electron that is taken from the water by breaking it into H+ ions and O-2 ions. These O-2 ions combine to form oxygen (O2) that is released into the atmosphere.
