The correct answer is D) it allows the alternator circuit breaker to be opened or closed remotely at the synchronizing panel. The "Gen. Bkr. Sw." (or Generator Breaker Switch) is a device that allows the operator to remotely open or close the alternator circuit breaker from the synchronizing panel. This is a common feature on marine electrical switchboards to provide remote control of the generator circuit breaker, which is an important safety and operational function. The other answer choices are incorrect because they describe functions that are not typically associated with a basic generator circuit breaker switch. The circuit breaker's overload, short circuit, and tripping functions are usually controlled by the breaker itself or its associated protective relays, not the remote switch.