What is a GFCI, and where is it required?

A Ground Fault Circuit Interrupter (GFCI) is designed to protect people from electrical shock by detecting imbalances between the incoming and outgoing current in a circuit. When it senses a ground fault, which could occur if water or moisture is present and a person becomes a path to ground, it quickly shuts off the electricity.

GFCIs are specifically required in areas where electricity and water may come into contact, such as kitchens, bathrooms, laundry rooms, and outdoor locations. This requirement is critical for safety, as the risk of electric shock increases significantly in wet environments.

In contrast, the other options illustrate devices or concepts that do not correctly describe a GFCI or its applications, which helps clarify why B is the most accurate choice.