The Respiratory Systems of Fishes, Frogs, Sponges, and Earthworms Are

The respiratory systems of fishes, frogs, sponges, and earthworms are similar in that they

A) have a countercurrent exchange system.
B) employ an extensive system of air sacs that ensures a unidirectional flow of air.
C) exchange gases across a moist respiratory surface.
D) have internal respiratory structures.
E) utilize a complex network of air-conducting tubes.