b. H2O ->S NADPH -> Calvin cycle
Explanation:
Photosynthesis can be compartmentalized into two phases: one that depends directly on the light - photochemical phase and one that does not depend on the light, called chemical phase.
The first uses H2O to produce ATP and a reduced electron carrier (NADPH + H +), the second uses ATP, NADPH + H + and CO2 to produce sugar. In the photochemical phase, light energy is used to produce ATP from ADP + Pi, through a set of reactions mediated by groups of molecules - the photosystems - in a cycle called photophosphorylation.
There are two types of photophosphorylation: one non-cyclic that produces NADPH and ATP and one cyclic that produces only ATP. In the chemical phase, which is not directly dependent on light, non-cyclic photophosphorylation products - NADPH and ATP - and CO2 are used to produce glucose, in the so-called Calvin-Benson cycle. Although it is also called the dark phase, it is not independent of light, since for the enzyme responsible for fixing CO2, RuBisCo, requires light to be reduced and to be in its active state.
