**Core Concept**
The management of pediatric cardiac arrest involves the use of electrical defibrillation to restore a normal cardiac rhythm. The American Heart Association (AHA) recommends the use of biphasic defibrillators, which are more effective than monophasic defibrillators in converting VF to a normal rhythm. The energy required for defibrillation is determined by the weight of the patient, with smaller children requiring lower energies.

**Why the Correct Answer is Right**
For children weighing between 1-25 kg, the recommended energy for biphasic defibrillation is 2-4 J/kg. Given that the child in question weighs 15 kg, the total energy required would be 30-60 J. However, the exact energy may vary depending on the specific defibrillator being used. In this scenario, an energy of 50 J would be an appropriate choice, as it falls within the recommended range and is a commonly used setting for pediatric defibrillation.

**Why Each Wrong Option is Incorrect**
**Option A:** Using an energy of 100 J would be excessive and may cause unnecessary cardiac damage.
**Option B:** Using an energy of 20 J would be insufficient and may not be effective in converting VF to a normal rhythm.

**Clinical Pearl / High-Yield Fact**
When using a defibrillator in a pediatric patient, it's essential to use the correct energy setting to avoid unnecessary cardiac damage. Always check the patient's weight and the defibrillator's settings before delivering a shock.

**Correct Answer:** C. 50 J