🔍 Key Concepts

• U.S. Inland River Aids to Navigation on the Upper Mississippi River • How to read a Light List entry (color, flash pattern, and period) • Difference between fixed lights and flashing lights and what "Fl(2) R 5s" would mean if you saw it in a book

💭 Think About

• Think about how you would use the Light List or river chart for mile 288.6 AHP to confirm the exact color, number of flashes, and period of Greenwood Light. • Ask yourself: does Greenwood Light on this stretch of river normally mark a bend/obstruction where a more attention‑getting characteristic (multiple flashes) might be used instead of a steady fixed light? • Consider the difference between a single flash and a group of two flashes, and whether a 4‑second or 5‑second period is more typical for that type of marker on inland rivers.

✅ Before You Answer

• Before choosing, be sure you can match all three elements: color, number of flashes, and total period (seconds). • Eliminate any choice where the flash group and period don’t look like a standard group‑flashing notation you might see in the Light List (for example, how "Fl R 4s" differs from "Fl(2) R 5s"). • Verify mentally whether a simple fixed light is likely at this location, or whether a group‑flashing light would better distinguish this aid from nearby lights on a busy river reach.