Why is defibrillation in the first few minutes of cardiac arrest so critical?

A) If cardiac arrest is not treated within the first few minutes, ventricular fibrillation will convert to asystole, a non-shockable heart rhythm.
B) Research has shown that a heart in cardiac arrest will continue to pump blood for a few minutes before cardiac output drops to zero.
C) In the first few minutes of cardiac arrest, the blood pressure is still normal, but will drop quickly, making successful defibrillation less likely.
D) In the first few minutes of cardiac arrest the heart is still warm, but begins to cool rapidly making it less receptive to a defibrillatory shock.

A