The light reactions convert light energy into chemical energy carriers, so the question is really asking what those carriers are, along with the one gas byproduct.
- $O_2$/NADH/$H_2$: $O_2$ is correct, water splitting at photosystem II does release oxygen. But the electron carrier reduced in photosynthesis is $NADP^+$, giving $NADPH$, not $NAD^+$ giving $NADH$ (that pairing belongs to respiration). No free hydrogen gas is released either.
- $O_2$/NADP$^+$/$CO_2$: $O_2$ is right, but $NADP^+$ is the oxidized form that gets used up as a reactant, not made as a product, and $CO_2$ is taken in (fixed) during the Calvin cycle; it is never a product of the light reactions.
- $O_2$/NADPH/ATP: $O_2$ comes from splitting water. $NADPH$ comes from reducing $NADP^+$ with the electrons freed at the end of the transport chain. $ATP$ comes from the proton gradient driving ATP synthase. All three are genuine products of the light reactions.
- $O_2$/NADP$^+$/ATP: $ATP$ and $O_2$ are right, but this option keeps $NADP^+$ in its oxidized form instead of the reduced $NADPH$ that the chloroplast actually hands off to the Calvin cycle.
Only the third option lists all three real products correctly: oxygen, reduced NADPH, and ATP.
Let's summarize:
- Water splitting at photosystem II gives $O_2$.
- Electron transport ends by reducing $NADP^+$ to $NADPH$.
- The proton gradient built across the thylakoid membrane powers ATP synthase to make $ATP$.
The products of the light reactions are $O_2$, $NADPH$, and $ATP$.