Cnidarians exhibit two basic body forms called polyp and medusa. Of these two, polyp is
free-swimming and umbrella-shaped
free-swimming and sessile
sessile and umbrella-shaped
sessile and cylindrical
Polyps are sessile and cylindrical (e.g., Hydra, Adamsia) whereas medusa is umbrella-shaped and free-swimming (e.g., Aurelia or jelly fish).