Which of the following descriptions about Portal authentication is incorrect?

Which of the following descriptions about Portal authentication is incorrect?
A . Portal authentication can be triggered in two ways: active authentication and passive authentication. Active authentication is initiated by the client, and passive authentication is initiated by the authentication server.
B . Under normal circumstances, the client does not need to install additional software and authenticates directly on the Web page, which is simple and convenient.
C . The Portal server can be an independent entity outside the access device (external Portal server), or it can be an embedded entity that exists within the access device (built-in Portal server)
D . The Portal authentication system mainly includes four basic elements, client, access device, Portal server and authentication server

Answer: A