If IP phone A fails to register with U1900, which of the following situations will not be the cause of the registration failure? ()
A . IP phone A has a network failure
B . The SIP server information in the configuration of IP phone A is incorrectly configured.
C . SIP account and password in IP phone A configuration are wrong
D . The user ID and phone number of IP phone A configured in the U1900 system are inconsistent
Answer: D