English

Kid

29 October, 13:46

29. Which of the following best describes animal

species that function as a "keystone" (line 35) ?

A. They are a major factor in disease

prevention.

B. They are a food source for other animals.

C. They pollinate every plant species.

D. They are crucial in maintaining the

balance of their ecosystem.

E. They generate the oxygen in the

atmosphere.