The dependent variable would be anything that is not consistent. So outside factors such as how much sun and the environment that the plant is contained in.
The answer is A. Putting the aquarium in the dark means that
the aquatic plants will not be able to photosynthesize. The process of photosynthesis produces oxygen
as a by-product. The oxygen is used by the fishes in respiration and release
carbon dioxide. The carbon dioxide is used by the aquatic plants in photosynthesis.
