Final answer:
A river with high flow, low salt concentration, and low oxygen concentration would have a low variety of organisms due to limited phytoplankton growth and low oxygen levels.
Step-by-step explanation:
A river with high flow, low salt concentration, and low oxygen concentration would have a low variety of organisms because these conditions do not support diverse aquatic life. The high flow of the river prevents the growth of phytoplankton, which are essential for the food chain. The low oxygen concentration also limits the survival of aquatic organisms, as they require oxygen for respiration.