A Patient's ECG Was Abnormal and the Physician Determined That

A patient's ECG was abnormal and the physician determined that a pacemaker was necessary Which of the following best describes the normal electrical functioning of the heart?

A) Electrical activity is initiated by the SA node and depolarization is carried from the ventricle by the AV node.
B) Electrical activity is initiated by the AV node and depolarization is carried from the atria by the SA node.
C) As the resting membrane potential decreases the SA node will reach its depolarization threshold.
D) As the resting membrane potential increases the AV node will reach its depolarization threshold.