Final answer:
The correct answer to what a survey buoy may have is a flashing red light, which is used to increase visibility and indicate surveying activity to passing vessels.
Step-by-step explanation:
The question pertains to the characteristics of a survey (special purpose mark) buoy. A survey buoy is a marker used at sea to indicate the area where surveying is occurring. The correct answer to the question A survey (special purpose mark) buoy __________ is B. may have a flashing red light. This means that these buoys can be equipped with red lights that flash to increase their visibility and to signal their significance to passing vessels, helping to prevent interference with the surveying activities.