Question

is the outermost covering of the long bones. periosteum endosteum medullary

Explanation:

The periosteum is a dense layer of vascular connective tissue enveloping the bones except at the surfaces of the joints. The endosteum is a thin vascular membrane of connective tissue that lines the inner surface of the bony tissue that forms the medullary cavity of long bones. The medullary cavity is the central cavity of bone shafts where red bone marrow and/or yellow bone marrow (adipose tissue) is stored. So, the outermost covering is the periosteum.

Answer:

Periosteum