Exam 300-810 topic 1 question 122 discussion

I think D is correct

https://www.cisco.com/c/en/us/support/docs/unified-communications/expressway-series/117811-configure-vcs-00.html#anc9 Voice Services Domain The user always logs in with userid@domain4, as there should be no difference in user experience when inside or outside. This means that if domain1 is different from domain4, you must configure the voice services domain in the Jabber client. This is because the domain portion of the login is used in order to discover the Collaboration Edge services using Service (SRV) record lookups. The client performs a Domain Name System (DNS) SRV record query for _collab-edge._tls.<domain>. This implies that when the domain from the login user ID is different than the domain from the Expressway E, you must use the voice service domain configuration. Jabber uses this configuration in order to discover the Collaboration Edge and the UDS.