BOTH INTERNATIONAL & INLAND Which vessel(s) is required to sound a fog signal of one prolonged followed by two short blasts?

Correct Answer: Option D — All of the above

Rule 35(c) mandates the signal of one prolonged followed by two short blasts for vessels not under command, restricted in their ability to maneuver, engaged in fishing, or sailing. This signal identifies vessels that have limited maneuverability, warning others to maintain a safe distance in restricted visibility.