Explanation: Navigational radar antennas typically rotate at relatively slow speeds, primarily to ensure sufficient "dwell time" on targets. Dwell time refers to the period during which the radar beam illuminates a particular area. A slower rotation speed allows the radar to transmit more pulses and receive more echoes from a given direction, improving signal-to-noise ratio, detection range, and the clarity of the displayed image, which are crucial for accurate navigation. Speeds in the range of 6 to 15 RPM provide a good balance between updating the display frequently enough for real-time navigation and allowing adequate dwell time for reliable target detection and mapping of the surrounding environment. Faster rotation speeds (C and D) would reduce dwell time, potentially decreasing detection range and detail, while option A includes slightly higher speeds that are less common for typical navigational systems.