The walls of heart chambers are made of a special muscle called ____________, which contracts continuously and rhythmically to pump blood.A、pericardiumB、 endocardiumC、 epicardiumD、 myocardium-易过题库-题库最全的搜题网站

The walls of heart chambers are made of a special muscle called ____________, which contracts continuously and rhythmically to pump blood.

Apericardium

B endocardium