A farmer digs a small pond in a pasture. The farmer adds young individuals from two species of
algae-eating fish to the ponds and plants some reeds around the edge of the pond. The farmer wants
the pond to be a sustainable ecosystem.
Which of the following would be most helpful in increasing the pond ecosystem’s sustainability?
a. Decreasing the number of plant species around the edge of the pond
b. Introducing older fish of the same species into the population of algae-eating fish
c. Having a greater diversity of living organisms in the pond
d. Adding gravel between the water and where the reeds are planted