Answer:
The correct answer will be option-C
Explanation:
Keystone species are the key species of any ecosystem which greatly influence the other species of the existing species of that habitat.
The keystone species are called so as without them other inhabiting species would be dramatically different or it could change the ecosystem.
The sea otters are considered the keystone species as they help maintain the population of the sea urchins as well as the kelp preyed by the sea urchins and also provide a home to other species.
Thus, Option-C is the correct answer.