Following a grounding, you can best determine that a SLACK fuel oil tank has been holed by __________.

Correct Answer: Option D — sounding the tank

Sounding the tank is the most direct and reliable method to detect hull breaches. If a tank is holed, the hydrostatic pressure differential will cause the level to change rapidly, either by leaking oil out or allowing seawater to ingress, which is immediately identifiable through manual or remote sounding systems.