1. YANG is primarily used to model the configuration and state data used by NETCONF operations.
2. NETCONF (RFC 6241) is an XML-based protocol that client applications use to request information from and make configuration changes to the device.
so B and C are both right, but C is a better answer according to Cisco.
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/datamodels/configuration/xe-16/data-models-xe-16-book/yang-netconf.html
1. YANG is primarily used to model the configuration and state data used by NETCONF operations.
2. NETCONF (RFC 6241) is an XML-based protocol that client applications use to request information from and make configuration changes to the device.
so B and C are both right, but C is a better answer according to Cisco.
NETCONF uses both xml and yang
yes but XML is not a data modeling language