Question 22 AB01 - Able Seafarer

The Correct Answer is B **Why option B ("May show a yellow light with a flashing rhythm") is correct:** Under the U.S. Aids to Navigation System (which follows the International Association of Marine Aids to Navigation and Lighthouse Authorities - IALA - standards for the ATONs it manages), a **Special Mark** is used to designate a special area or feature, such as traffic separation schemes, spoil grounds, cable or pipeline crossings, measured mile courses, etc. Special Marks are distinguished by their **yellow** color. If lighted, the light must also be **yellow**. The characteristics assigned to Special Marks are typically non-standard rhythms (not used for lateral or cardinal marks), and the most common characteristics are **flashing (Fl)**, single-group flashing (e.g., Fl(3)), or continuous flashing (Quick or Very Quick). Therefore, a yellow light with a flashing rhythm is the standard and acceptable characteristic for a Special Mark. **Why the other options are incorrect:** * **A) Must be lighted with a fixed or flashing white light:** This is incorrect. Special Marks must use a **yellow** light. White lights are generally reserved for non-lateral marks, fixed shore lights, or specific cardinal marks (if unlit during the day), but not Special Marks. * **C) May show a light with the Morse code "A" rhythm:** This is incorrect. The Morse code "A" (short-long, or $\dot{-}$) is the specific, reserved light characteristic for a **Safe Water Mark** (used to designate open water or the centerline of a channel). Special Marks must not use this characteristic to avoid confusion. * **D) Must be lighted with a yellow isophase light:** This is incorrect. While the light must be yellow, it is not required to be an isophase (Iso) light (a light where the period of illumination and darkness are equal). Special Marks are permitted to use a wide variety of yellow characteristics, including flashing (Fl), single-group flashing, or continuous rhythms, but they are not *required* to be Iso. "May show" (Option B) is correct, whereas "Must be" (Option D) is too restrictive and therefore incorrect.