The organisms attached to the substratum, generally, possess (a) one single opening of the digestive canal (b) cilia on the surface to create water current (c) radial symmetry (d) asymmetrical body.
Option C The organisms attached to the substratum possess radial symmetry in all vertical planes. All the animals belonging to cnidaria (e.g. jellyfish) and echinodermata (e.g. starfish) are radially symmetrical and typically sessile in their adult form. In radial symmetry the parts in an organ or organism when cut through the centre in any direction produces two halves that are mirror images of each other
