What Would Happen If Your SA Node and AV Node

What would happen if your SA node and AV node fired at same time?

A) Your blood pressure would increase.
B) The QRS wave on an ECG would disappear, as it would be masked by the P wave.
C) The volume of blood leaving the ventricles would decrease.
D) Blood would be forced back into the atria from the ventricles.
E) The T wave on an ECG would disappear, as it would be masked by the QRS wave.