Consider a single electron's movement through the light reactions. Put these steps of the light reactions in the correct order
from this electron's perspective:
1. Light excites the electron in photosystem I.
2. Light excites the electron in photosystem II.
3. The electron reduces NADP+ to NADPH.
4. The electron passes through an electron transport chain, which helps generates a H+ gradient used to make ATP.
steps 2, 4, 1,3
steps 1, 2, 3, 4
steps 2, 3, 1,4
steps 1, 4, 2, 3

The light dependent reaction of photosynthesis involves the production of ATP and NADPH needed for the next stage of photosynthesis (Calvin cycle) to produce sugars. The light stage occurs in the thylakoid membrane of the chloroplast, which contains certain complex pigments called PHOTOSYSTEM.

The order or electron flow in the light stage is as follows:

- Light excites the electron in photosystem II to split water into hydrogen and electrons.

- Light excites the electron in photosystem I and loses its electrons to the final electron acceptor, NADP+

- The electron reduces NADP+ to NADPH

- The electron passes through an electron transport chain, which helps generates a H+ gradient used to make ATP from ADP as catalysed by ATP synthase