Which might NOT be considered a keystone species in its habitat?

Question

Quizplus · Accepted Answer

All of the answers could be considered keystone species in their habitats as they all play important roles in maintaining the overall health and balance of the ecosystem. A prey species may help regulate the population of other species, a predator species may help control the abundance of prey species, plants that feed insects may provide important food resources for a variety of organisms, and insects that pollinate plants are critical for the reproduction of many species of plants.

Which Might NOT Be Considered a Keystone Species in Its