Diffusion is the random movement of molecules or particles from a region of high concentration to a region of low concentration bringing a natural flow in the system. Diffusion ensures that there is a state of equilibrium in the number of molecules in the system.
The pair of characteristics that one must use to classify a fish is the presence of jaw and skeleton type. Agnatha fishes are also called jawless fishes and they lack bony skeletons. Cartilaginous fishes are composed of cartilage skeletons. Bony fishes have bony skeleton structures.
Migration is D, the seasonal movement of organisms between locations!
