During daylight hours black double-cone topmarks are the most important feature of cardinal marks. Which of the four topmarks shown in illustration D030NG below indicates the best navigable water lies to the west of the buoy?

Correct Answer: Option C — C

In the IALA system, a Western cardinal mark features two cones pointing away from each other (apex to apex). This configuration indicates that the deepest water or the safest passage lies to the west of the buoy, allowing mariners to clear the hazard on the indicated side.