The Person Has a Pacemaker That Creates a Pacer Spike

The person has a pacemaker that creates a pacer spike before each QRS on the ECG when the intrinsic heart rate falls below 70. What is the significance of this? It is:

A) abnormal, because the asynchronous pacemaker is not maintaining the heart rate.
B) normal, because the asynchronous pacemaker is responding to the heart rate change as designed.
C) normal, because the demand pacemaker is responding to the heart rate drop at the preset level.
D) abnormal, because the demand pacemaker is not effectively pacing both the atria and ventricle.