Final answer:
The light-dependent reactions in photosynthesis require NADP+, which is reduced to NADPH to carry energy for the synthesis of glucose in the Calvin cycle.
Step-by-step explanation:
In plants, the light-dependent reactions of photosynthesis require a molecule to accept electrons and hydrogen ions to form NADPH, a molecule that carries energy and electrons for the next stage of photosynthesis. The correct answer to the question is C. NADP+, which is reduced to NADPH during the light-dependent reactions. These reactions take place in the thylakoid membranes of chloroplasts and use light energy to convert water and NADP+ into oxygen, ATP, and NADPH. The ATP and NADPH produced are then used in the Calvin cycle to fix CO2 into organic sugar molecules, like glucose.