Which type of buoy typically includes a unique sound signal for identification?

The correct choice indicates the type of buoy that includes a unique sound signal for identification. Cardinal marks are specifically designed to indicate the safe side of navigational hazards or to help mariners understand their position relative to the hazard. These buoys employ sound signals that can vary in characteristics to differentiate among the cardinal directions—north, south, east, and west. This auditory signaling assists in navigation, especially in conditions of low visibility.

In contrast, safe water marks, special mark buoys, and port hand marks do not typically include a distinctive sound signal. Safe water marks signify that there is navigable water all around them but do not have an associated sound signal like cardinal marks do. Special marks are used for various special purposes and may also not feature sound signals unless specified for a particular use. Port hand marks primarily provide navigational guidance to indicate a safe passage on the port side but do not involve unique sound signals for identification like the cardinal marks do.