Some Relatively Large Multicellular Aquatic Animals Have No Circulatory System

Some relatively large multicellular aquatic animals have no circulatory system.One way that these organisms manage gas exchange is by

A) bringing the external environment into a branched system of channels such that most cells are close to that environment.
B) hosting endosymbiotic bacteria that produce oxygen inside their tissues.
C) breathing air into a set of lungs.
D) basking at the surface periodically to allow for diffusion of oxygen.
E) having long diffusion distances.