If you hear a single prolonged blast every two minutes, which vessel condition are you most likely observing?

Answer: A — Power-driven vessel making way in fog

In restricted visibility, sound signals tell other vessels what you’re doing. A power-driven vessel that is underway and making way uses a single prolonged blast at intervals not more than two minutes. So hearing one prolonged blast every two minutes indicates a motor vessel moving ahead. This cadence is specific to a vessel under power and making way, distinguishing it from vessels under sail, at anchor, or being towed, which follow different signal patterns.