The answer would be:
b. Diaphysis
Here is more about the diaphysis:
Long bones have 2 main parts. You have the diaphysis and the epiphysis. The diaphysis is the long hollow shaft that is made up of compact hard bone. The ends of the long bond, which are wider are the epiphysis.
Inside the long bone you have the medullary cavity and this is filled with yellow bone marrow and red blood cells are produced here.
Make sure that you spend extra time warming up during a workout
Generally, they should D. Recall the equipment to save future patients from having the same issues and to prevent a class action lawsuit from being filed against them.