What does this command do?

router(config)# ip port-map user-1 port tcp 4001

A.
enables application firewall inspection on a user-defined application that is mapped to TCP port 4001

B.
enables NBAR to recognize a user-defined application on TCP port 4001

C.
enables the Cisco IOS Firewall to inspect TCP port 4001 as part of the ip inspect name xxx TCP inspection rule

D.
defines a user application in the PAM table where the user-defined application is called “user-1” and that application is mapped to TCP port 4001