What is the Address field value ‘securelogin.arubanetworks.com’ used for?

Refer to the exhibit.

When configuring a Web Login Page in ClearPass Guest, the information shown is displayed.

What is the Address field value ‘securelogin.arubanetworks.com’ used for?
A . for ClearPass to send a TACACS+ request to the NAD
B . for appending to the Web Login URL, before the page name
C . for the client to POST the user credentials to the NAD
D . for ClearPass to send a RADIUS request to the NAD
E . for appending to the Web Login URL, after the page name.

Answer: C