pany has implemented 802.1X authentication as a security enhancement.  Which statement is  true about 802.1x port-based authentication？（）

• A、 TACACS+ is the only supported authentication server type.
• B、 If a host initiates the authentication process and does not receive a response， it assumes it is  not authorized.
• C、 RADIUS is the only supported authentication server type.
• D、 Before transmitting data， an 802.1x host must determine the authorization state of the switch.
• E、 Hosts are required to havea 802.1x authentication client or utilize PPPoE.
• F、 None of the other alternatives apply.