What was the question for this implicit rationale, and corresponding answer?
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.
The answer: (D)
The question: What are a source of food for many fish species?
Options:
- (A) layers of fat
- (B) bird species
- (C) human species
- (D) keystone species
- (E) Organic compounds
- (F) barnacles
- (G) gastropod shells
- (H) species of deer