Refer to the partial output of the show interfaces command:

What does the Serial 0 is administratively down, line protocol is down line indicate with certainty?

A.
There is no problem with the physical connectivity.

B.
There is a configuration problem in the local or remote router.

C.
There is a problem at the telephone company’s end.

D.
The shutdown interface command is present in the router configuration.

Explanation:
The Serial 0 is administratively down, line protocol is down line in the output of the show interfaces command indicates the following:
– The shutdown interface command is present in the router configuration. This indicates that the administrator might have manually shut down the interface by
issuing the shutdown command.
– A duplicate Internet Protocol (IP) address might be in use.
This line does not show that there is no problem with the physical connectivity. Since the interface is administratively shut down, there is no way of determining the

operational status of the physical layer.
The Serial 0 is administratively down, line protocol is down line does not indicate a configuration problem in the local or remote router. A problem in the configuration
of local or remote router would be indicated by the Serial 0 is up, line protocol is down message.
This line does not show that there is a problem at the telephone company’s end. Since the interface is administratively shut down, there is no way of determining the
operational status of the physical layer or protocol layer on the other end of the line.
Objective:
Infrastructure Maintenance
Sub-Objective:
Use Cisco IOS tools to troubleshoot and resolve problems

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/interface/command/ir-cr-book.html