Answer:
b. number of aquatic plants
Explanation:
The number of aquatic plants doesn't increase the demand for oxygen in water because these plants take in carbon dioxide rather than oxygen. This means that an increase in their number will not trigger an increase demand for oxygen, rather it will trigger an increase demand for carbon dioxide in its dissolved form.
An increase in the concentration of solid waste, increases the demand for oxygen because it is needed for decomposition.
An increase in aquatic animals will increase the demand for oxygen in its dissolved form because aquatic animals take in oxygen to survive.
An increase in the flow of water increases the demand for oxygen because as water flows, it mixes with air. The more rapid it is, the higher the chance to mix with oxygen.