Multiple choice Which of the following is a set of representative organisms of class Hydrozoa? Hydra, Obelia and Aurelia Obelia, Aurelia and Pennatula Physalia, Aurelia and Pennatula Obelia, Physalia and Hydra Hydra, Pelagia and Adamsia Reveal answer Fill a bubble to check yourself D Correct answer Explanation Correct answer. Obelia, Physalia and Hydra: All are members of class Hydrazoa of phylumn Coelentrata.