Final answer:
A GFCI protects you by detecting leakage currents in an electrical circuit and instantly cutting off electrical flow(option a), with the standard set to react if leakage exceeds 5 mA.
Step-by-step explanation:
A Ground Fault Circuit Interrupter (GFCI) is designed to protect you by detecting any leakage of current in an electrical circuit and then quickly cutting off the electrical flow to prevent harm. The way a GFCI works is based on the principle of electromagnetic induction.
The device constantly monitors and compares the current levels in the live/hot and neutral wires. In a normally functioning circuit, the current in these wires should be equal. If the GFCI detects that the current in the neutral wire is less than in the live/hot wire, it concludes that leakage current is occurring, possibly through an unintended path, which could be hazardous.
GFCIs are typically programmed to interrupt the circuit if the leakage current exceeds 5 milliamperes (mA), which is the accepted limit for a maximum harmless shock. This function ensures safety even if the leakage current is being safely directed to the ground through an intact ground wire. The GFCI will still trip to prevent potential electric shock. By tripping, or disconnecting the circuit, the GFCI enforces the repair of the leakage.
Additionally, for manual testing or resetting of the device, a GFCI does include a reset button. Therefore, the correct answer to how a GFCI protects you is that it detects when there is any current leakage and cuts off the electrical flow to prevent electrical shock.