A yellow buoy may mark which of the following?

A yellow buoy is primarily used to indicate a special caution area. These buoys serve to alert operators to potential hazards such as underwater obstructions, the presence of swimming areas, or other conditions that require a heightened level of attention and care while navigating.

In the context of the options presented, while a yellow buoy can be associated with various navigational messages, it is specifically designed to denote caution and does not typically mark the end of a no-wake zone, area limits for anchorage, or explicitly indicate a restricted area. Understanding these signaling functions is crucial for safe boating practices, as they guide boaters in navigating safely and respecting the designated uses of water areas.