An electrocardiogram (ECG) can be used to record the electrical conduction of the heart. Which of the following statements accurately represents the features of an ECG?

a. The QRS complex is the represents the electrical activity associated with the depolarization of the atrial muscle.
b. You cannot observe atrial repolarization on an ECG because the P wave hides it.
c. The P wave represents the electrical activity associated with the depolarization of ventricular muscle.
d. The T wave represents the electrical activity associated with the repolarization of the ventricles.