🔍 Key Concepts

• U.S. lateral buoyage system (IALA-B) – how red vs green marks indicate the channel sides when returning from seaward or heading upstream on rivers • The difference between shape and color of dayboards: triangles vs squares, and which side of the channel they mark • Meaning of AHP (Above Head of Passes) on the Mississippi River system and what is considered the "returning" direction

💭 Think About

• Decide whether a light at a river mile marked AHP would normally be on the returning (upstream) side or the seaward (downstream) side of the channel • Recall the "Red Right Returning" rule and translate that into which color and which shape you’d expect to see on that side of the channel as a dayboard • Match that expected color/shape combination with the closest choice in the list

✅ Before You Answer

• Be sure you know which direction is considered returning on the Mississippi River (mileages like 943.6 AHP increase in which direction?). • Confirm from your memory: on the returning side, are the fixed aids/dayboards triangles or squares, and what color? • Eliminate any options that pair a color with the wrong shape for that side of the channel (e.g., a color that should be square but is shown as a triangle, or vice versa).