Which Cisco IOS XR BGP configuration command is required to enable MP-BGP to carry IPv6 VPN routes?

Which Cisco IOS XR BGP configuration command is required to enable MP-BGP to carry IPv6
VPN routes?

A.
address-family ipv4 unicast

B.
address-family ipv6 unicast

C.
address-family vpnv4 unicast

D.
address-family vpnv6 unicast

Explanation:
http://www.cisco.com/en/US/tech/tk872/technologies_configuration_example09186a0080b3e11d.s
html