Answer:
D. Photosynthesis
Step-by-step explanation:
There is carbon dioxide from the atmosphere going to the tree from arrow C.
There is sunlight from the sun going to the tree from arrow A.
Carbon dioxide and sunlight and 2 of the reactants in the photosynthesis equation.
Photosynthesis:
6CO2 + 6H2O → C₆H₁₂O₆ + 6O₂
This means that the reactants, six carbon dioxide molecules and six water molecules, are converted by light energy captured by chlorophyll (implied by the arrow) into a sugar molecule and six oxygen molecules, the products.