text: The<unk><unk>  of the<unk> , directed downward and slightly backward, is formed by the ventricles, and rests upon the central tendon and a small part of the left muscular portion of the diaphragm.
  It is separated from the base by the posterior part of the coronary sulcus, and is traversed obliquely by the posterior longitudinal sulcus.
option_0: Diaphragmatic surface of heart
option_1: Left margin of heart
option_2: Apex of the heart
option_3: Right border of heart
option_4: Sternocostal surface
option_5: Mediastinal surface of lung
option_6: Serous pericardium
option_7: Floating rib