Which of the following is an input for the light-independent stage of photosynthesis?

The light-independent stage of photosynthesis, also known as the Calvin cycle, utilizes several inputs to synthesize glucose from carbon dioxide. One of the critical inputs is NADPH. During the light-dependent reactions of photosynthesis, light energy is used to split water molecules, which leads to the production of ATP and NADPH. These molecules are then used in the Calvin cycle as reducing agents and energy sources. NADPH provides the necessary electrons for the reduction of carbon compounds, which is essential for the formation of glucose.

In contrast, the other options listed do not serve as inputs for the light-independent stage. Oxygen is a byproduct of the light-dependent reactions, glucose is a product of the light-independent reactions, and water is primarily involved in the light-dependent stage where it is split to produce the energy carriers ATP and NADPH. Thus, NADPH is indeed the proper input for the light-independent stage, highlighting its essential role in the photosynthesis process.