BOTH INTERNATIONAL & INLAND A tug is towing three unmanned barges astern in fog. The third vessel of the tow should sound __________.

Correct Answer: Option B — no fog signal

Under COLREGS Rule 35(c), only the last vessel of a tow, if manned, sounds a fog signal. Unmanned barges cannot sound signals, and intermediate vessels remain silent to prevent confusion regarding the number of units in the tow.