What sound signal should be given by a sailboat underway in fog?

A sailboat underway in fog is required to sound a specific signal to alert other vessels of its presence and movement. The correct answer is a prolonged blast followed by two short blasts, which should be sounded every two minutes.

This signal is mandated by maritime navigation rules to enhance safety in situations with low visibility, such as fog. The prolonged blast serves to indicate the presence of the vessel and its type, while the two short blasts communicate its movement or intention to maneuver. Adhering to this signaling convention is crucial for preventing potential collisions and ensuring clear communication among vessels operating in restricted visibility conditions.

Other options do not align with international or local boating regulations regarding sound signals for different types of vessels. For instance, one short blast every minute is typically used by powered vessels, while two prolonged blasts relate to specific situations, such as vessels at anchor or in circumstances that differ from those governing a sailboat underway in fog. Thus, option B encompasses the appropriate action for a sailboat navigating in such conditions to maintain safety on the water.