BOTH INTERNATIONAL & INLAND In a dense fog you hear a whistle signal ahead of one prolonged blast followed by three short blasts. This signal indicates a __________.

Under Inland Navigation Rules, for the condition where 'In a dense fog you hear a whistle signal ahead of one prolonged blast followed by three short blasts. This signal indicates a', the correct requirement is: 'manned vessel being towed'. This standard ensures clear navigational intent and collision avoidance.