BOTH INTERNATIONAL & INLAND While underway in a fog you hear a signal of three strokes of a bell, a rapid ringing of the bell, and three more strokes of the bell. This signal is made by a vessel __________.

Under Inland Navigation Rules, for the condition where 'While underway in a fog you hear a signal of three strokes of a bell, a rapid ringing of the bell, and three more strokes of the bell. This signal is made by a vessel', the correct requirement is: 'aground'. This standard ensures clear navigational intent and collision avoidance.