Light Reactions : ATP :: Calvin Cycle :
a. G3P
b. H2O
c. O2
d. H+

a. G3P

Explanation:

Photosynthesis is the process by which plants synthesize their food from inorganic sources in the presence of light. The photosynthetic process occurs in two stages namely: light dependent stage (light reaction) and light independent stage (Calvin cycle).

The light stage primarily functions to synthesize ATP and NADPH products needed in the Calvin cycle to synthesize sugar (glucose). However, the CALVIN CYCLE produces a three-carbon compound called GLYCERALDEHYDE-3-PHOSPHATE (G-3-P) as one of the precursors of glucose.