The ping loopback hangs with no output. Which of the following is the most likely cause？（）

• A、The loopback interface is down and resolv.conf is configured.
• B、The loopback is not in /etc/hosts and resolv.conf is configured.
• C、The loopback interface is down and resolv.conf is not configured.
• D、The loopback is not in /etc/hosts and resolv.conf is not configured.