A stalked, sessile marine organism has several feathery feeding structures surrounding an opening through which food enters. The organism could potentially be a cnidarian, a lophophorate, a tube-dwelling worm, a crustacean, or an echinoderm. Which of the following traits, if found in this organism, would allow the greatest certainty of identification?

a nervous system
the presence of what seems to be radial symmetry
a digestive system with mouth and anus separate from each other
a hard covering made partly of calcium carbonate
a water vascular system