On small passenger vessels, when must watchmen patrol throughout the vessel to guard against and give alarm in case of fire or other danger?

Correct Answer: Option B — During the nighttime when the vessel carries overnight passengers

46 CFR 185.510 mandates that on small passenger vessels carrying overnight passengers, a watchman must patrol the vessel during nighttime hours. This requirement ensures early detection of fire or other emergencies, providing a critical safety layer for passengers who are asleep and vulnerable to hazards.