What is a cause of this?

A network engineer troubleshoots a provisioned RAP backup SSID issue that occurs when a user tries to connect to the Internet from a hotel. The engineer lists the connection and sees backup SSID from an AP broadcast. The engineer can connect to it receives an IP address from the RAP’s DHCP pool, but the captive portal of the hotel will not come up. The backup SSID is always there, and the enterprise SSID does not appear.

What is a cause of this?
A . The RAP does not Source NATs user traffic.
B . The hotel blocks IKE protocol on the hotel edge firewall.
C . The hotel blocks UDP port 4500 on the hotel edge firewall.
D . The RAP is added into the RAP whitelist of the controller.

Answer: D