BOTH INTERNATIONAL & INLAND While underway in fog, you hear a vessel ahead sound two prolonged blasts on the whistle. You should __________.

Correct Answer: Option B — sound only fog signals until the other vessel is sighted

COLREGS Rule 35 requires power-driven vessels underway making way in restricted visibility to sound fog signals of one prolonged blast at intervals not exceeding 2 minutes. Two prolonged blasts indicate a power-driven vessel stopped and making no way.