To harden one of the servers, an administrator needs to remove the possibility of remote administrative login via the SSH service. Which of the following should the administrator do?

A. Add the line DenyUsers root to the /etc/hosts.deny file.
B. Set PermitRootLogin to no in the /etc/ssh/sshd_config file.
C. Add the line account required pam_nologin. so to the /etc/pam.d/sshd file.
D. Set PubKeyAuthentication to no in the /etc/ssh/ssh_config file.