What protects a circuit when a meter is being installed?

The correct choice is breakers. When installing a meter, circuit breakers serve as a crucial safety mechanism that protects electrical circuits from overloads and short circuits. They are designed to automatically interrupt the flow of electrical current when they detect an abnormally high current that could potentially cause damage to the circuit or create fire hazards.

Fuses also play a protective role by breaking the circuit when current exceeds a certain threshold, but they must be replaced after they blow, while breakers can be reset easily after tripping. Disconnects are used to completely isolate a circuit for maintenance or safety reasons, but they do not provide ongoing circuit protection while work is performed. Relays, on the other hand, are used to control electrical circuits but are not designed primarily for protection during installations. Therefore, breakers are specifically suited for protecting the circuit during the installation of a meter.