Which pair of characteristics would you use to place a fish in one of the three fish classes: agnatha, cartilaginous fishes, or bony fishes?

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.