Answer:
The correct option is D) Keystone
Explanation:
In environmental studies, a keystone animal can be described as one of the most vital element or animal or a particular community. In a food chain, the keystone animal is of particular importance and if it is removed then the entire food chain will be affected by it.
In the scenario discussed in the question, Cheetahs are the keystone animals. Their absence will result in the disruption of the entire ecosystem of the forest. Hence, option D is correct.