What are a source of food for many fish species?\nOptions:\n- (A) layers of fat\n- (B) bird species\n- (C) human species\n- (D) keystone species\n- (E) Organic compounds\n- (F) barnacles\n- (G) gastropod shells\n- (H) species of deer
Reason slowly and give your answer.
(D)
Sponges are a source of food for many species of fish.

Sponges are also keystone species.

Keystone species are a source of food for many fish species.

.

Therefore, the answer is (D)