When paralleling two alternators using three synchronizing lamps, the flickering of all three lamps becomes progressively slower and slower. What does this mean?

Correct Answer: Option C — The frequency of the incoming generator is approaching that of the bus.

Progressively slower lamp flickering indicates that the slip frequency is decreasing, meaning the incoming alternator's speed and frequency are converging toward the live bus frequency in preparation for safe manual synchronization per IEEE 45 guidelines.