What is the default mode supported by WatchGuard AP devices on the 5GHz band?

The correct answer is founded on the compatibility and capabilities of the 5GHz band supported by WatchGuard Access Points (AP). The default mode of 802.11 A/N Mixed allows devices that operate either in the older 802.11 A standard or the newer 802.11 N standard to connect seamlessly. This is crucial for environments that utilize a mix of legacy and modern wireless devices because it ensures that all devices can communicate without being limited to just one protocol.

The mixed mode supports both standards, maximizing flexibility and coverage within the network. It enables improved data rates and performance associated with the 802.11 N standard, while still accommodating the established performance of 802.11 A. This adaptability is beneficial in varied real-world deployment scenarios where networks must serve a range of devices.

The other options would restrict the connectivity to specific standards. For instance, if only 802.11 A were selected, modern devices using 802.11 N would be unable to connect, leading to potential connectivity issues. Thus, the default mode of 802.11 A/N Mixed is the most advantageous configuration for a diverse range of client devices in the 5GHz spectrum.