"d" would also be my answer. I used to use TCP wrappers in the /etc/inetd.conf file but since I can now enter address ranges in the new /etc/xinetd.conf I have less need to mess with /etc/hosts.allow. Of course other services like NFS, portmap, etc can still be restricted in the hosts.allow file. And iptables/ipchains is another way to restrict connections (firewall). But 'd' should be the correct answer for this question. Watch us be wrong for some stupid reason. If we're wrong it wouldn't be because the question is outdated.
