80. In the northeastern Pacific ocean, sea otters occur at a relatively low abundance. By preying upon sea urchins, sea otters maintain underwater kelp (large algae) "forests", which would otherwise be decimated by the herbivorous sea urchins. The kelp forests supply food for a wide variety of marine organisms, as well as providing refuge from predation and nursery habitat for juveniles. Based on this, what type of species best describes sea otters?
(A) indicator species
(B) flagship species
(C) keystone species
(D) dominant species