Reconstruct a question, answer pair from this explanation: Echinoderms have a unique water vascular system with tube feet. Another group of echinoderms are the echinoids. Echinoids have unique water vascular system was tube feet.
Q:Which has a unique water vascular system?
Options:
- (A) roots
- (B) trees
- (C) Conifers
- (D) Echinoids
- (E) fur seals
- (F) Most plants
- (G) ferns
- (H) bushes
A:(D)