You are traveling upstream on a river at dusk. You see a buoy with the number 5 and a flashing green light. What should you do?

If you see a buoy with the number 5 and a flashing green light while traveling upstream on a river, you should keep the buoy on your starboard (right) side. The green light indicates that you are approaching a navigational marker, and maintaining this position will help ensure safe passage. Continue to monitor your surroundings and proceed cautiously, especially as it is dusk and visibility may be reduced.