Question

why are carbon dioxide levels changing in the tube with elodea?
a. carbon dioxide levels are dropping because carbon dioxide is a product in photosynthesis
b. carbon dioxide levels are dropping because carbon dioxide is a reactant in photosynthesis
c. carbon dioxide levels are dropping because carbon dioxide is dispersing into the atmosphere
d. carbon dioxide levels are dropping because carbon dioxide is reacting with the phenol red

Explanation:

Elodea is a plant that undergoes photosynthesis. In photosynthesis, carbon - dioxide is a reactant that is used up to produce glucose and oxygen. So, carbon - dioxide levels drop in the tube with Elodea.

Answer:

B. Carbon dioxide levels are dropping because carbon dioxide is a reactant in photosynthesis