🔍 Key Concepts

• Special marks in the U.S. Aids to Navigation System (IALA B) • Standard color and light color used for special marks • Difference between yellow aids and aids using Morse code "A"

💭 Think About

• Which type of mark in the system is specifically associated with Morse code "A"—is it a special mark or something else? • What light colors are typically used for lateral, safe water, isolated danger, and special marks? Which of those use yellow? • In the options, which describe things that are optional/may be used versus mandatory/must be used for special marks?

✅ Before You Answer

• Confirm in the Light List or AtoN manuals what color and light color define a special mark • Check which buoy type is defined by Morse "A" (· −) in the Nav Rules/AtoN references • Be sure whether special marks have a required light rhythm or only permitted light characteristics (note the words "may" vs. "must").