Answer:
Carbon dioxide, water, sunlight.
Step-by-step explanation:
Photosynthesis uses the energy in sunlight to drive the reactions that produce glucose. These reactions are necessary for the algae to produce food, continue to survive, and grow.
As well as sunlight, photosynthesis requires carbon dioxide and water as reactants. The reaction produces glucose and releases oxygen as a byproduct.
The algae need an adequate supply of all of these reactants to grow in abundance.