Question

Water vascular system is the unique character of ________.
a) Echinodermata
b) Arthropoda
c) Protochordata
d) Mollusca

Answer 1

The water vascular system is a unique and defining characteristic of echinoderms.

so option A is the correct answer

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Answer 2

Water vascular system is the unique character of (a) Echinodermata.

It is a water based hydraulic system used for movement, food intake, and excretion along with respiration.  

The system is made of canals and it connects plenty of tube feet.

The precise structure of this system largely varies between the classes of Echinodermata.

It functions as the part of the coelomic cavities of echinoderms.