Vernon is using the diagram shown below to develop a model of photosynthesis. The letters A, B, and C each represent a reactant or product of the process. In the light-dependent reactions, light strikes the oval thylakoids. Compound A enters the thylakoid, and compound B leaves it. In the light-independent reactions, compound C enters a cycle in the stroma, and sugars leave the cycle. ATP and NADPH cycle between the two sets of reactions.

Should water (H2O) be included in the model as a reactant or product? If so, how should it be included?

A. Yes, as reactant A.
B. Yes, as product B.
C. Yes, as reactant C.
D. No, it should not be included.