You get a call that the Internet is down. When you investigate the Internet router and perform a show interface serial 0/0, you see the following status. What might be the problem?

Serial0/0 is administratively down, line protocol is up
Hardware is MCI Serial

A. The serial line connecting to the ISP is down.
B. Someone accidentally shut down the serial interface.
C. Routing to the ISP is not set correctly.
D. The clocking from the ISP has stopped.

B. It is most likely, since the interface was working before, that someone shut down the interface with the shutdown command. This can be seen in the show interface serial 0/0 command; the interface is reporting it is administratively shut down.