Which of the following is correct?
A. The endocardium is the membrane that lines the interior of the heart. It is made up of a thin, smooth layer of cells that resembles the squamous epithelium in the walls of the oral cavity.
B. The myocardium is the thinnest layer of the cardiac muscle. It is responsible for pumping the blood through the blood vessels.
C. The epicardium is the thin, outermost layer of the heart wall that extends with the fibrous sac enclosing the body.
D. All of the above.​