Question: What is the format of the XCAP Root URI when a UE has an ISIM with a domain name from the IMPI ending in "3gppnetwork.org"?
Option 1: http://xcap.<MNC>.<MCC>.pub.3gppnetwork.org
Option 2: http://xcap.<domain_name_from_IMPI_except_last_two_labels>.pub.3gppnetwork.org
Option 3: http://xcap.<all_labels_of_domain_name_from_IMPI_except_last_two>.pub.3gppnetwork.org
Option 4: http://xcap.<MNC>.<MCC>.ims.3gppnetwork.org
Explanation: According to the text, when a UE has an ISIM with a domain name from the IMPI ending in "3gppnetwork.org", the XCAP Root URI should be created by taking all labels of the domain name from the IMPI except the last two, and appending ".pub.3gppnetwork.org".