BOTH INTERNATIONAL & INLAND You are underway in fog and you hear one prolonged blast followed by two short blasts. This is a vessel __________.

Correct Answer: Option D — towing

Under Inland Navigation Rules, for the condition where 'You are underway in fog and you hear one prolonged blast followed by two short blasts. This is a vessel', the correct requirement is: 'towing'. This standard ensures clear navigational intent and collision avoidance.