Since A, B, and C belong to different orders, and D, E and F belong to the same order, the latter are more closely related and thus are expected to show a greater degree of structural homology. They are closer to their common ancestor than A, B and C.
The skeletal system works as a support structure for your body. It gives the body its shape, allows movement, makes blood cells, provides protection for organs and stores minerals. The skeletal system is also called the musculoskeletal system.
