Why Is Photosynthesis a Coupled Reaction

Why is photosynthesis a coupled reaction?

A) Photosynthesis requires two reactants: carbon dioxide and water.
B) Sunlight energy enters a plant and is ultimately lost as heat.
C) The exergonic reaction occurs in the plant, and the endergonic reaction occurs in the sunlight.
D) The exergonic reaction occurs in the plant, and the endergonic reaction occurs in the soil.
E) An exergonic reaction occurs in the sunlight, and an endergonic reaction occurs in the plant.