BOTH INTERNATIONAL & INLAND While underway in fog you hear another vessel sounding two prolonged blasts every two minutes. This signal indicates a vessel __________.

Correct Answer: Option A — drifting

Under Inland Navigation Rules, for the condition where 'While underway in fog you hear another vessel sounding two prolonged blasts every two minutes. This signal indicates a vessel', the correct requirement is: 'drifting'. This standard ensures clear navigational intent and collision avoidance.