What is the shaft of a long bone?

a. endosteum

b. periosteum

c. diaphysis

d. epiphysis

$\textbf{Endosteum}$ = membrane structure that lines the medullary cavity

$\textbf{Periosteum}$ = membrane structure which consists of dense fibrous tissue covering a long bone everywhere except at joint surfaces

$\textbf{Diaphysis}$ (or the $\textit{shaft}$) = part of the bone which is a hollow tube made of hard compact bone

$\textbf{Epiphysis}$ = part of the bone at its end