On Cisco IOS XR software, which two of the address-family command options in IS-IS
configuration mode are valid? (Choose two)

A.
address-family clns

B.
address-family ipv4 unicast

C.
address-family ipv6 unicast

D.
address-family vpnv4

E.
address-family vpnv6

Explanation:
http://www.cisco.com/en/US/docs/ios_xr_sw/iosxr_r3.8/routing/command/reference/rr38isis.pdf
To enter address family configuration mode for configuring Intermediate System-to-Intermediate
System (IS-IS) routing that use standard IP Version 4 (IPv4) and IP Version 6 (IPv6) address
prefixes, use the address-family command in router configuration or interface configuration mode.
To disable support for an address family, use the no form of this command. Address family {ipv4 |
ipv6} {unicast | mulitcast} no address-family {ipv4 | ipv6} {unicast | multicast}