I'll give you a question, please answer with step-by-step reasoning process.
Which has a unique water vascular system?\nOptions:\n- (A) roots\n- (B) trees\n- (C) Conifers\n- (D) Echinoids\n- (E) fur seals\n- (F) Most plants\n- (G) ferns\n- (H) bushes

(D)
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.

.

Therefore, the answer is (D)