For configuring wireless access for multiple classes of IoT devices with varying security requirements, using a single SSID with Multiple Pre-Shared Keys (MPSK) is an efficient solution. MPSK allows different devices or groups of devices to connect to the same SSID but with unique PSKs, facilitating unique security policies for each class. Given that some IoT devices only support 802.11b, which operates in the 2.4GHz band, it is essential to include the 2.4GHz band in the configuration. The 5GHz band should also be included to support devices capable of operating in that band and to optimize network performance. The 6GHz band (option A) is not suitable since 802.11b devices are not compatible with it. Individual SSIDs for each IoT class (options C and D) would unnecessarily complicate network management and SSID overhead.