BOTH INTERNATIONAL & INLAND While underway in fog, you hear a signal of one prolonged blast followed by three short blasts. Which vessel is required to sound this signal?

Correct Answer: Option D — A vessel being towed (manned)

Rule 35(c) explicitly requires that a vessel being towed, or if more than one vessel is towed, the last vessel of the tow, if manned, shall sound one prolonged blast followed by three short blasts at intervals of not more than two minutes to indicate her presence.