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.