Explanation
The correct answer is (B) Keystone species.
Keystone species are species that have a significant impact on their ecosystem and play a crucial role in maintaining the balance and structure of the entire community. These species have a disproportionately large influence on the ecosystem relative to their abundance or biomass. Their presence or absence can have cascading effects on other species and ecological processes. Keystone species often have a strong influence on regulating populations of other organisms, controlling community dynamics, and promoting biodiversity. Examples of keystone species include predators that regulate prey populations or species that create and modify habitats.
