Final answer:
The shaft of a long bone is called the diaphysis, which is the tubular shaft that contains the medullary cavity filled with yellow marrow and is surrounded by compact bone.
Step-by-step explanation:
The shaft of a long bone is called the diaphysis. The diaphysis is the tubular shaft that runs between the proximal and distal ends of the bone. The medullary cavity within the diaphysis contains yellow marrow and the walls of the diaphysis are made up of dense, hard compact bone.
The epiphysis is the wider section at each end of the bone, filled with spongy bone and red marrow. The epiphyseal plate, also known as the growth plate, is a layer of hyaline cartilage found in growing bones, situated at the metaphysis - the narrow area between the diaphysis and the epiphysis. As a person reaches early adulthood and the bone stops growing, the epiphyseal plate is replaced by osseous tissue, becoming an epiphyseal line. Therefore, in the context of the shaft of the long bone, the correct answer is option B. Diaphysis.