The correct answer is B) The stalled generator's circuit breaker will trip on reverse power. When two generators are operating in parallel, if one engine driving a generator shuts down, the stalled generator will start to act as a motor, drawing power from the remaining running generator. This will cause the stalled generator's circuit breaker to trip on reverse power to protect the system from damage. The other answer choices are incorrect because: A) Both generators would not immediately shut down, C) The running generator would not motorize, and D) The running generator's circuit breaker would not immediately trip on overload, as the system is designed to handle the loss of one generator through the reverse power trip of the stalled generator's circuit breaker.