The correct option is 4: Bilaterally symmetrical. Adult echinoderms (like starfish, sea urchins, and sea cucumbers) are famously defined by their radial symmetry, often specifically pentaradial (five-part) symmetry. However, a key concept in the study of the phylum Echinodermata is that this radial symmetry is a secondary, evolutionary adaptation, typically linked to their sessile or slow-moving bottom-dwelling lifestyle. The correct option, Bilaterally symmetrical, refers to the morphology of the echinoderm…Read More