In the film, Paine recalls that a year after the starfish had been removed, the number of species decreased from 15 to eight, after three years the number went down to seven, and after another seven years it was almost all only mussels. In the control plots, the number and diversity of species were basically unchanged. Which statement(s) best explain(s) these results? a. Keystone species are critical to the diversity and stability of an ecosystem.

b. When a predator is removed, the prey of that predator always increases, and species not eaten by the predator always decrease.

c. The disappearance of producers from an ecosystem can cause the number of predators to increase