According to the Rules of the Road, a vessel underway and making way in fog shall sound every two minutes—

• A. one prolonged blast.
• B. two short blasts.
• C. one short blast.
• D. three prolonged blasts.

Answer: (A)

In fog, ships use specific whistle signals to convey their status to others, so everyone can anticipate actions in limited visibility. For a vessel that is underway and making way, the required signal is a single prolonged blast, repeated at intervals of not more than two minutes. This long, continuous sound clearly communicates that you are moving and present, helping other vessels gauge your presence and speed so they can maneuver safely around you.

The other options don’t fit this particular rule. Two short blasts and three prolonged blasts are associated with different situations or signals and do not match the standard indication for a moving vessel in fog.