Answer:
b. a producer species
Step-by-step explanation:
Every trophic level is important, each level is reliant on the one below it for a food source. However, the producers are the base-line when it comes to food energy, providing food for prey, who thus provide food for predators. If the producer species in an ecosystem were to be removed, then the prey die off, thus the predators, causing a total collapse in the ecosystem.
hope this helps !!