On a small passenger vessel, if an inlet or discharge pipe is not accessible, its shut off valve __________.

Correct Answer: Option D — All of the above

46 CFR 182.520 requires that shut-off valves for inaccessible inlet or discharge pipes must be operable from the weather deck, clearly labeled, and identifiable regarding their closing direction. These measures ensure that the crew can quickly isolate hull penetrations during flooding emergencies, even if the valve location is obstructed.