The correct option is A Both A and R are correct and R explains A
Most species co-evolve in their natural habitat; therefore most organisms have deep-rooted and sometimes obligate relationships with other species in their habitat, for e.g., an obligate predator, parasite or a pollinator. When one such organism is lost, their relationships are also lost, thereby threatening the survival of other species that are associated with it, either through mutualistic, predatory or parasitic relationships.