What was the question for this implicit rationale, and corresponding answer?
Echinoderms have a unique water vascular system with tube feet. Each starfish arm is lined with tube feet. Starfish are an echinoderm with a unique water vascular system.
 The answer: (C)
The question: What is an example of an echinoderm?
Options:
- (A) a fish
- (B) eel
- (C) starfish
- (D) parasites
- (E) ferns
- (F) shark
- (G) fertile
- (H) algae