If delegated credentials checking has been enabled and remote workers can register to the Expressway, which statement is true?

If delegated credentials checking has been enabled and remote workers can register to the Expressway, which statement is true?
B . 323 message credential checks are delegated.
C . SIP registration proxy mode is set to On in the Expressway.
D . A secure neighbor zone has been configured between the Expressway and the Expressway Control.
E . SIP registration proxy mode is set to Off in the Expressway.

Answer: D