What do flashing yellow lights indicate while underway with regard to dredging operations?

Answer: B — dredge pipeline

Flashing yellow lights while underway indicate the presence of a dredge pipeline. This signaling is crucial for ensuring the safety of navigation around dredging operations, as it alerts other vessels to the specific area where dredging equipment or pipelines may be deployed. Such lights serve to warn mariners of potential obstructions or hazards created by these operations, which could pose dangers to navigation if not clearly marked. By understanding that flashing yellow lights correspond with dredging activities, mariners can take appropriate actions to navigate safely and avoid collisions or interference with dredging work. Recognizing these signals is part of maintaining situational awareness in busy or potentially hazardous waters where dredging is taking place.