Which of the following can best eliminate dial-up access through a Remote Access Server as a hacking vector?

Which of the following can best eliminate dial-up access through a Remote Access Server as a
hacking vector?

A.
Using TACACS+ server

B.
Installing the Remote Access Server outside the firewall and forcing legitimate users to
authenticate to the firewall.

C.
Setting modem ring count to at least 5

D.
Only attaching modems to non-networked hosts.