A Patient Has Been Admitted After the Insertion of a Pacemaker

A patient has been admitted after the insertion of a pacemaker because of bradycardia. She asks what third-degree heart block is, and the nurse replies

A) "Coronary blood vessel occlusion causing slow contraction of the right ventricles."
B) "Sclerosis of cardiac valves causing slow pulse."
C) "A defect in AV junctions slows and impairs conduction of impulses from the SA node to the ventricles."
D) "Increased pressure in the pulmonary vessels."