To protect systems and life, GFCI systems monitor which of the following?

A Ground-Fault Circuit Interrupter (GFCI) continuously monitors the current balance between the “hot” and “neutral” conductors. If an imbalance greater than about 5 milliamps occurs (indicating leakage current flowing to ground), the GFCI trips instantly to protect personnel from shock.

Correct (D): Current – GFCIs detect differences in current between conductors.

Incorrect: Resistance (A), Voltage (B), and Power (C) are not directly monitored by GFCIs.