On a Cisco 9800 wireless LAN controller, an engineer must create a new SSID and configure authentication using a pre-shared key. Which controller profile should be edited?

The WLAN profile is the correct choice because it defines the SSID, security settings (like pre-shared keys or 802.1X), and other client-facing parameters for a wireless network. When creating a new SSID and configuring its authentication method, you directly modify the WLAN profile associated with that SSID. Policy profiles define client access policies and QoS, but not the SSID itself or its authentication. RF profiles control radio-specific settings like power and channels. Flex profiles are used for FlexConnect deployments, which manage AP behavior in remote branches, not the core SSID configuration.